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January 9, 2015
After a mild December (11th warmest since 1895 on a statewide basis), the other shoe dropped over the first full week of January, with temperatures averaging from 7 to 10 degrees F colder than average through the first seven days of the month, somewhat analogous to the start of January last year. Brimson (St Louis County) reported the coldest temperature in the nation on January 4th with -28F and on January 5th Togo (Itasca County) reported the coldest in the nation at -29F. In fact over the first week of the month a few records were set:
New low temperature records included: -28F at Thief River Falls on January 4th; and -28F at Grand Portage on January 5th
New cold maximum temperature records include: -7F at both Grand Marais and Grand Portage on January 5th; and -8F at Wright (Carlton County) also on January 5th
In addition a new daily precipitation record was set for January 3rd at International Falls with 0.58 inches (associated with 7.8" of snow)
Read on ....

Mode of action of Neonicotinoids

Karl Foord, Extension Educator - Horticulture

Photo 1: Paired nerves


Photo 2: Neural synapse


Insecticides can be characterized by the way in which they disrupt important biochemical functions. Many insecticides target the nervous system of insects by imparing the control of neural transmission. This can be done by disabling the system, and shutting it down. However, the majority of neural insecticides put the system in a continual state of ON giving the organism no opportunity to stop neural transmission. This results in uncontrolled and uninterrupted nerve firing. The insect that is exposed to such chemicals exhibits tremors, hyperactivity and convulsions. Sublethal doses of these chemicals can impair proper functioning behaviors such as flight orientation, and feeding while greater doses lead to a quicker death.

Normal neural transmission

A normal neural transmission proceeds down the nerve axon which splits into branches and eventually into smaller branches called dendrites. The dendrites of one nerve cell pair with the dendrites of other cells. The space between these two dendrites is call a synapse (Exhibit 1).

The electrical signal of the nerve is translated into a chemical message made up of so called neurotransmitter molecules. These molecules diffuse across the synapse and attach to receptor molecules on the dentrites of the paired nerve (Exhibit 2). The chemical message is translated back into an electrical message that then travels down this nerve cell's axon, and the neurotransmitter molecules are disassociated from the receptor molecules by an enzyme.

Neonicotinoid disruption of neural impulse

Neonicotinoid molecules enter the neural synapse and irreversibly attach to the receptors on the receiving neuron (Exhibit 2). The neurotransmitter enzyme cannot remove the imidacloprid molecule and the receptor is thus continuously active. The organism has lost control of neural transmission and either loses function or dies.

Mary H. Meyer, extension horticulturist and professor, University of Minnesota

Mary Meyer

Table 1: BEST Crabapples for Minnesota

References and Further Reading:

Beckerman, J., J. Chatfield, and E. Draper. 2009. A 33-year Evaluation of Resistance and Pathogenicity in the Apple Scab-crabapples Pathosystem. HortSci. 44(3):599-608.

Chatfield, J. A. E. A. Draper, and B. Cubberley. 2010. Why Plant Evaluations Matter. American Nurseryman 210(9):10-15.

Draper, E. K., J. A. Chatfield, and K. D. Cochran. 2005. Marvelous Malus--Ten Crabapples Worthy to Know, Show, and Grow. Brooklyn Botanic Garden. Accessed October 6, 2014.

Green, T. L. 1995. Results of the national crabapple evaluation program. Accessed online October 3, 2014.

Green, T.L. 1996. Crabapples--When you're choosing one of those apple cousins, make flowers your last consideration. Amer. Horticult. 75:18-23.

Guthery, D.E. and E.R. Hasselkus. 1992. Jewels of the landscape. Amer. Nurseryman 175(1):28-41.
Iles, J. 2009. Crabapples..... With No Apologies. Arnoldia. Accessed online October 10, 2014.

Koetter, R. and M. Grabowski. 2014. Managing apple scab on ornamental trees and shrubs. Accessed online October 10, 2014.

Romer, J., J. Iles, and C. Haynes. 2003. Selection Preferences for Crabapple Cultivars and Species. HortTechnology 13:522-526.

Schmidt, J. Frank and Sons. 2014. Crabapple Information Chart. Accessed online October 8, 2014.

Mary H. Meyer, extension horticulturist and professor, University of Minnesota

Mary Meyer

Photo 1: Adirondack close-up

Mary Meyer

Photo 2: Adirondack - whole tree

Mary Meyer

Photo 3: Beverly close-up

Mary Meyerd

Photo 4: Beverly - Whole tree

Mary Meyer

Photo 5: Bob White close-up

Mary Meyer

Photo 6: Bob White - whole tree

Mary Meyer

Photo 7: Donald Wyman - whole tree

Mary Meyer

Photo 8: Firebird close-up

Mary Meyer

Photo 9: Firebird - whole tree

Mary Meyer

Photo 10: Louisa close-up

Mary Meyer

Photo 11: Louisa - whole tree

Mary Meyer

Photo 12: Pink Spires close-up

Mary Meyer

Photo 13: Pink Spires - whole tree

Which one would I plant in my yard? Anyone from this list, but something in the name 'Professor Sprenger' does resonate with me! It is a lovely tree that greets visitors on the Snyder Terrace at the Arboretum. Others you can see easily at the Arboretum are: 'Donald Wyman' planted in mass in the first parking lot bay across from the Oswald Visitor Center; 'Adirondack' marks the entrance to the espalier in the Cloister Herb Garden; 'PrairiFire' makes the double allée at the Sensory Garden, 'Pink Spires' flanks the entry to the new Green Play Yard at the Andrus Learning Center, and two 'Prairie Maid' trees fill an island in the staff parking lot.

Mary H. Meyer, extension horticulturist and professor, University of Minnesota

Mary Meyer

Photo 1: Prairie Maid close-up

Mary Meyer

Photo 2: Prairie Maid - whole tree

Mary Meyer

Photo 3: PrairiFire close-up

Mary Meyerd

Photo 4: PrairiFire - Whole tree (left) Sargentii espalier (right)

Mary Meyer

Photo 5: Professor Sprenger close-up

Mary Meyer

Photo 6: Professor Sprenger - whole tree

Mary Meyer

Photo 7: Red Jewel close-up

Mary Meyer

Photo 8: Red Jewel - whole tree

Mary Meyer

Photo 9: Royal Raindrops close-up

Mary Meyer

Photo 10: Royal Raindrops - whole tree

Mary Meyer

Photo 11: Sargentii close-up

Mary Meyer

Photo 12: Sugar Tyme close-up

Mary Meyer

Photo 13: Sugar Tyme - whole tree

This summer I was asked so many times "What is wrong with my crabapple?" that I started LOOKING anew at crabapples. 2014 was a banner year for apple scab, discoloring the foliage and causing premature leaf and even fruit drop. Affected plants looked dormant, or as many homeowners feared, dead. Apple scab can weaken trees, but rarely is fatal. Scab may allow secondary organisms to attack the tree and can decrease its winter hardiness, so it is best to purchase a scab-resistant crabapple. WHICH crabapples are resistant to scab, is complicated as the newest study (Beckerman et al, 2010) shows a new strain of this disease may now infect previously resistant cultivars. Additionally, we tend to think only about the FLOWERS on crabapples, and especially LOVE the showy pink or red flowers that are unfortunately often more susceptible to scab.

I recommend the first criteria for selecting a crabapple should be the ultimate SIZE, height and shape of the plant, followed by scab resistance, fruit, and finally the flowers. It is a misconception that crabapple fruit is messy: the small colorful fruit (5/8 inch or less) is a valuable food source sought by birds throughout the winter, and adds color and interest for many months.

Late fall is an ideal time to walk the crabapple collection at the Minnesota Landscape Arboretum and pick your favorite, because you can easily select scab resistant plants with clean, healthy leaves. Additionally, you can evaluate the fruit which varies widely in color and can last for MONTHS, easily six or even eight months. Remember that crabapple flowers last only for DAYS, perhaps a week. Why not select a crabapple for healthy leaves, and attractive fruit and just let the flowers be an added bonus?

From endless lists of hundreds of crabapples, the short list below was developed based on fall appearance with clean foliage at the Arboretum. Additionally, these plants are also top recommendations from long-term research trials conducted at the Ohio State University (their Crablandia field plots); Morton Arboretum, Illinois; Purdue University, Indiana; and the multi-state National Crabapple Trials.

I propose these 13 crabapples as "the best" for Minnesota. If your favorite is not here, let me know! All of the plants listed show good to excellent resistance to apple scab with an asterisk * for those showing some susceptibility to the new apple scab strain now in the Midwest. 'Red Splendor' is a showy red-pink prolific flowering crabapple that originated in Minnesota, however, it is susceptible to scab, needs plenty of space due to its large size and can be defoliated and defruited in mid-summer due to scab.

Which one would I plant in my yard? Anyone from this list, but something in the name 'Professor Sprenger' does resonate with me! It is a lovely tree that greets visitors on the Snyder Terrace at the Arboretum. Others you can see easily at the Arboretum are: 'Donald Wyman' planted in mass in the first parking lot bay across from the Oswald Visitor Center; 'Adirondack' marks the entrance to the espalier in the Cloister Herb Garden; 'PrairiFire' makes the double allée at the Sensory Garden, 'Pink Spires' flanks the entry to the new Green Play Yard at the Andrus Learning Center, and two 'Prairie Maid' trees fill an island in the staff parking lot.

There is an amazing variation that exists in these tough plants. A crabapple that grows well in Ohio, may not show the same disease resistance to apple scab here in Minnesota. The weather and climate makes a difference. Touring the famous crabapple collection at the Arboretum and the newer plantings in the display gardens can give you a first-hand look at how the plants grow in our climate. Ideally, we would annually rate crabapples three times: for foliage and fruit in September and October; for winter interest and fruit (bird food) in January; and flowering in May. Look for yourself at a garden center or the Arboretum, so you can decide which form and fruit is best for your garden and landscape.

Turf and Bees: What's the buzz on pesticides in lawns?

By Ian Lane, Graduate Research Assistant

If you have been paying attention to the news lately, you know that bees have been making headlines. News outlets have done an amazing job of helping scientists sound the alarm on unsettling declines in bee pollinators. While we have good evidence for declines in honey bees and some of their cousins, the bumble bees, the cause of this decline is hard to pinpoint. Current thinking in the scientific community puts the decline down to a number of interacting factors, including reduction in stable food sources, introduction of bee diseases, and the irresponsible use of insecticides. While it's difficult to tease apart how these factors interact, we do have some good knowledge about how lawns fit into this theoretical framework.

Sam Bauer

Photo 1: White clover and dandelion can provide great early season forage for pollinators in lawns


Lawns are home to a number of weeds that are the bane of homeowners. While our gut reaction may be to reach for a herbicide, it's worth noting that many weeds actually can provide high quality forage for bees. Two of the most important lawn forage plants are the common dandelion (Taraxacum officinale) and Dutch white clover (Trifolium repens). Dandelions are one of the earliest, and often only, blooming flowers of spring. This early source of pollen and nectar is essential to overwintering honey bee colonies as they begin the process of raising new workers. White clover is another spring bloomer (though not as early) that provides highly nutritious pollen throughout the year. While the exact nature of bee's relationship with these flowers isn't widely studied, recent research at the University of Kentucky sought to characterize the types of bees visiting dandelions and clover. They found surprising diversity on white clover, including a number of at risk bumble bees (Larson et al. 2014). Similar preliminary research here at the University of Minnesota confirms many of their findings.

There may also be some solutions for homeowners looking to control weeds but leave clover in their lawn. One common herbicide known as 2,4-D is effective on many broadleaf weeds, but generally ineffective on clover. Small demonstration trials at the University of Minnesota confirm that 2,4-D has relatively low action on clover but is relatively effective against other weeds.


The another type of pesticide that can make a big impact on bees are insecticides . Much of the recent attention on pollinators has focused on a class of insecticides known as the neonicitinoids. Neonicitinoids are used in turf to help control a number of insect pests, most importantly grubs. They work by "dissolving" into the irrigation water or rain, which is then taken up by the plant and becomes part of the leaf and root tissue. This ensures that any insect munching on the tissues of your grass gets a lethal dose, and your lawn stays green. While bees would never have a reason to take a bite of your grass, your helpful lawn weeds are a different story. It turns out that not only do these insecticides move into plant leaves and roots, but the nectar and pollen of the flowering weeds as well.

Many studies have looked to see if neonicitinoids applied to lawns full of clover have negative effects on bumblebee colonies. The researchers in Kentucky do this by getting a colony of the commercially available common eastern bumble bee (Bombus impatiens), placing it on a patch of flowering clover that is treated with a neonicitinoid, then caging them so they are forced to forage on the treated clover. These experiments are always accompanied with a similar set-up but on a non-treated patch as a point of comparison. Here again the University of Kentucky has been leading the way with a study published in 2002 (Gels et al. 2002) that found if imidacloprid (a type of neonicitinoid) was applied to flowering turf without any post application irrigation that bumble bee colonies suffered worker weight loss, increased worker death, and sluggish behavior. However, if irrigation was applied directly following these imidacloprid applications, no negative responses were seen.

Similar responses were seen in a study investigating clothianidin, another type of neonicitinoid (Larson et al. 2013). Bumble bee colonies that were confined over patches of flowering clover, and that had the high label rates of clothianidin applied to the turf, saw dramatic effects on the number of workers, new queens, as well as total colony weight when compared to control colonies. The effects of irrigation were not part of this study, but when clover nectar from nearby sights that had been applied with clothianidin were sampled, they found high amounts of the neonicitinoid. This study's main aim was to compare clothianidin to a new chemistry of insecticides called anthranilic diamide (specifically chlorantraniliprole). This new class of chemical had seemingly no adverse effects on bumble bee colonies when compared to the controls. While there is more research to be done, this is a promising alternative to neonicitinoids for insect control in turf. You can currently purchase chlorantraniliprole for use on residential and commercial turf, and trade names include "Scott's Grubex" or Syngenta's "Acelepryn".

While urban landscapes and lawns are only one part of a very large system, they are nevertheless an important part of a vast majority of people's lives. Promoting animal diversity in urban landscapes, be it pollinator or other, helps improve important issues related to stormwater runoff (rain gardens and buffer strips) and urban agriculture (pollination and biocontrol services) and also enriches everyday life through learning opportunities and aesthetic value. Even the smallest effort, such as leaving some weedy flowers or choosing a safer insecticide, may make a difference.

Stay Informed

A new series on pollinators is being offered by the University of Minnesota Landscape Arboretum. "Pollinators: What you need to know and how to make a difference" is a 3-part series focusing on: 1) Plants and People, 2) Pesticides and Other Problems, and 3) Policies and Politics.

The Minnesota Turf and Grounds Foundation will be offering a 1-day session on Super Tuesday of the Northern Green Expo, January 13th, 2015. "Bee Aware: The importance of pollinators in the landscape" will feature expert presenters discussing real world issues surrounding pollinators, as well as practical strategies to promote them in the landscape. Stay tuned to as this program develops.

Works Referenced

Gels, J. A., D. W. Held, and D. A. Potter. 2002. Hazards of Insecticides to the Bumble Bees Bombus impatiens (Hymenoptera : Apidae ) Foraging on Flowering White Clover in Turf. J. Econ. Entomol. 95: 722-728.

Larson, J. L., A. J. Kesheimer, and D. A. Potter. 2014. Pollinator assemblages on dandelions and white clover in urban and suburban lawns. J. Insect Conserv. 18: 863-873

Larson, J. L., C. T. Redmond, and D. A. Potter. 2013. Assessing insecticide hazard to bumble bees foraging on flowering weeds in treated lawns. PLoS One. 8: e66375.

Karl Foord, Extension Educator - Horticulture

Watching these bees leave their nest and returning covered with pollen was quite enjoyable.

I will let the video speak for itself. Please enjoy. Colletes foraging.

Karl Foord, Extension Educator - Horticulture

One of our early emerging vernal native bees is in the genus Colletes. These bees are commonly called plasterer bees, cellophane, or polyester bees. This is because the bee builds an underground nest and then paints/applies/lines her nest with a cellophane-like plastic material secreted from an abdominal gland. The bee applies this material with her two-lobe tipped tongue. This secretion helps protect the developing bees from fungal disease and acts as a waterproof barrier. It is so effective that ground-nesting species can occupy areas prone to flooding.

I photographed a Colletes bee digging a nest. The nest took several hours to dig which I videoed and then cut out much of the inactivity to create a 5 minute video.

One of today's landscaping rules-of-thumb is to cover bare soil with mulch to both prevent erosion and discourage weed encroachment. This makes sense, however should we reconsider this practice in light of our need to provide nesting habitat for native bees? Perhaps there are areas in the garden or proximal to the garden which could be left open and undisturbed.

Though not specifically stated open soil areas were considered a sign slovenlyness, something not tolerated in my upbringing environment. Somewhat along the line of "There are no dirty or lazy Zimmerman's". Something my maternal grandmother used to say.

The two main threats to most pollinators include habitat loss and pesticide use.

You can create a welcoming environment to ground nesting bees by doing the following:

1. Leave bare patches of ground in your garden or yard to help provide nesting sites. It may look unkempt but it is unkempt with a purpose.

2. Plant a variety of bee friendly nectar and pollen rich native plants. A good place to start is "Plants for Minnesota Bees" by Elaine Evans.

Elaine Evans

Photo 1: Plants for Minnesota Bees (front)

Elaine Evans

Photo 2: Plants for Minnesota Bees (back)

3. I have decided that to the extent possible I would rather watch what is happening in my garden then attempt to kill certain pests with the high likelihood of killing beneficials. My worst garden pest is the fourlined plant bug which attacks my anise hyssop. Given how I feel about anise hyssop (possibly the best bee plant I have encountered) you can imagine how motivated I would be to remove these pests. I have controlled them to my satisfaction by clapping my hands on the leaves where I see the bugs. The leaves tolerate this much more than the fourlined plant bugs. Avoiding the use of synthetic pesticides in your garden and on your lawn is recommended.

Butterflies in slow motion flight

Karl Foord, Extension Educator - Horticulture

I recently took a class on bee identification at the Southwest Research Station of the Museum of Natural History in the Chiricahua Mountains three hours west of Tucson, Arizona.
While traveling to one of the bee collection sites we passed a large puddle along the road. Two days previously a heavy downpour had soaked the countryside and this puddle downstream from an open cattle range provided the butterflies with water, sodium, and perhaps other needed nutrients.

I have always wondered about the flight of butterflies. Their flight often seems quite erratic. I understand this to be part of a strategy to avoid predators. Is their flight actually as erratic as it appears to us?

I returned to the puddle the following day and was happy to see that it was not completely dry. I was able to slow down their flight with a high speed camera capturing 3500 frames per second. If 30 frames per second is what we consider to be normal then this slows down the flight by a factor of 117.

What was seemingly erratic now seems quite graceful. Wouldn't you agree?

Notice how the wings curl to provide lift on both the forward and backward strokes of the wings. Also notice how the butterflies wing strokes are not constant and that they often drift before beginning a new stroke. Access the video at Butterflies in slow motion flight

Please enjoy the ballet.

Thanks for listening!

We aren't always able to answer everyone's text'd questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources.

Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

Question: Paver stone patio on north side of house has mold / moss in between stones. How do I get rid of this?

Answer: You can use a sharp tool to scrape / dig out moss and fill in spaces with builders' sand. You can plant low-growing, creeping plants like creeping thyme or wooly time in the spaces.

Mold can be removed with a bleach / water solution and a wire brush. Be careful not to get bleach on the plants nearby, your clothing or patio furniture.

Question: I just planted a 2" Autumn Blaze maple. What are you recommendations for watering?

Answer: Here is an excerpt from the U of M Extension publication Planting and Transplanting Trees and Shrubs (Gillman et. al):

Newly planted plants require routine watering. Typically, 5-7 gallons, applied to the root ball once a week, is an appropriate quantity of water to add to a newly planted tree or shrub; however, differing soil and weather conditions will affect the frequency with which water must be added. Examine the soil moisture 4-8 inches deep to determine the need for water. If the soil feels dry or just slightly damp, watering is needed. Soil type and drainage must also be considered. Well-drained, sandy soil will need more water, and more often than a clay soil that may hold too much water. A slow trickle of the garden hose at the base of the plant for several hours or until the soil is thoroughly soaked is the best method. Short, frequent watering should be avoided as this does not promote deep root growth but rather, the development of a shallow root system that is vulnerable to several environmental stresses.

Be sure to consult this publication for additional information about planting trees.

Question from Anne in Apple Valley: On my 'William Baffin' roses, the leaves turned yellow with brown spots, then dropped. Bare canes are still green. Is this fungal and should I treat before winter? Should I prune the canes back to the a foot from the ground and clean up to try and avoid re infection next spring? These are large 7- yr old plants and don't want to lose them.

Answer: It sounds as though your rose has black spot. Here is a good publication Rose Diseases (Pfleger et. al). Black spot on rose is a fungal disease caused by splashing water onto leaves. We had a rainy spring and summer and thus this was a "good" year for such diseases. Note that sanitation is a good place to start in reducing the occurrence next year. Treatment occurs during the growing season when the first signs of the disease occur. It is not appropriate to treat now. Diseased canes should be cut back a few inches into healthy wood. You can also help reduce water droplets that can foster fungal spores by watering at the base of the plant and mulching the roots. Space out the canes as you tie them to your trellis / fence so air can circulate, drying off leaves and canes. 

Question: Should a Fat Albert spruce be fertilized now?

Answer: Stop fertilizing trees and shrubs in mid-summer. Fertilizing now will cause new growth to occur that can be damaged by cold temperatures. Water evergreens now up until you cannot water any longer. This will reduce the chance of desiccation and browning of needles. More on evergreens

Question: Can I prune the water shoots off my crab apple now? How often can we prune to preserve size and shape?

Answer: Crab apple trees should be pruned once a year in late winter while still dormant. This will reduce infestations by pests and all the plant to heal the cut wound more quickly when it begins actively growing in early spring. Remove water shoots and selectively prune branches to open up the canopy, allowing air and light to reach the inner branches and buds. Protect the tree from animal damage in the winter by surrounding the trunk with hardware cloth fencing or corrugated plastic tubing. More on pruning trees.

Question: How do I know when to re-pot a ZZ plant?

Answer: Zamioculcas zamiifolia or "ZZ plant" is not one of the plants I know well, I admit. After some reading, I found out it is a rainforest plant, but has about 3-4 months of dry conditions. The plant apparently does not do well when pot-bound / crowded; hence, it may stop developing new leaves and stems. That may be the indicator that it's time to re-pot. It is apparently an excellent houseplant that grows well indoors and has few if any pest issues. It may drop its leaves once a year and appear dead, but that is apparently just its dormant behavior. Soil should be well-drained. It does not need much fertilizer - either a slow release balanced fertilizer every three months or a very dilute liquid fertilizer (1/4 strength) when you water.

Pollinator Habitat

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: Home landscape

Karl Foord

Photo 2: Home landscape

Karl Foord

Photo 3: Home landscape

Karl Foord

Photo 4: School landscape

Karl Foord

Photo 5: School landscape

Karl Foord

Photo 6: Business landscape

Karl Foord

Photo 7: Industrial landscape

Karl Foord

Photo 8: Industrial landscape

Karl Foord

Photo 9: Roadside setback for industrial landscape

Karl Foord

Photo 10: Undeveloped area

Karl Foord

Photo 11: Wild Bergamot (Monarda fistulosa) with bumblebee

Karl Foord

Photo 12: Hoary Vervain (Verbena stricta) with bumblebee

One of the factors in the decline of pollinators is the loss of habitat. To get a sense of this I took the position of a bee looking for forage. I drove my car from my house through my neighborhood in Chaska, Minnesota around the Chaska Middle School out to Hwy 41 and north toward Hwy 5 and the Minnesota Landscape Arboretum.

What I found in this casual survey was a preponderance of turf in the landscape. The homes had most turf surroundings with a few shade trees and low maintenance foundation shrubs. There were a few flowers to accent a rock or a mailbox. Often these plants were not attractive to pollinators such as daylilies. The businesses had turf and accented their signs with rocks and low maintenance plants. The industrial area was completely dominated by turf and shade trees, and contained no cultivated flowers.

The place where I found bee forage was in refuse areas or undeveloped areas. Here I found typical weeds such as thistle (Cirsium spp.), Queen Anne's Lace (Daucus carota), Bird's Foot Trefoil (Lotus corniculatus) among others. I also found Wild Bergamot (Monarda fistulosa), Hoary Vervain (Verbena stricta), and Grey-headed Coneflower (Ratibida pinnata). The majority of bees including bumble bees and other natives were working the beebalm and the vervain, predominantly.

Incidently the richest area was the undeveloped area along Hwy 41. I was informed that this was destined to be developed.

As a bee searching for forage this is rather discouraging with the future looking even more bleak. All things considered it still looks like one of the more promising solutions is to follow Dr. Marla Spivak's exhortation to plant flowers and specifically those that provide nectar and pollen to our pollinators.

There are many subtle and complex interactions between plants and their pollinators.
Can our combined urban spaces be designed in such a way as to substitute for the loss of natural areas as we humans continue to expand?

I do not know. However, it is in our best interest to try. As Marla says, "Plant Flowers!".

Planting a "Smart Snacks" garden

Each year, the Minnesota Landscape Arboretum Education staff designs and plants a IMG_1761.JPGTeaching Garden on-site focused on programming about food with titles like "Veggies by the Yard", and "Grow A Healthy Handful". Interpretive signage is always important to provide walk-by learning to visitors. These programs and the signage as well as plant lists, construction details, and tips for teaching are made available as teaching materials to Extension Master Gardeners the following year.

With all the interest in protecting pollinators, coupled with the need for people to eat healthier, the "Smart Snacks" garden idea was born. It was IMG_1763.JPGtrialed in the Teaching Garden (now called the Extension Master Gardener Teaching Garden), and this year was made available to Master Gardener volunteers. Five signs highlighting specific messages were made available as well - how tomatoes are pollinated, growing plants for pollinators, healthy tomato stats. Plant lists included cherry tomatoes, verbena, basil, mint, zinnia - and photos of examples as well as resources for materials. Smart Snacks gardens can be planted anywhere including in a "pop-up garden" format planted in a collapsible "bag" pot placed on asphalt or cement. The goal? To get people planting to support their own snacking and that of pollinators!

I chose to plant my own Smart Snacks garden along our driveway in two raised beds / P1250824.JPGretaining walls each about 48" x 72". I had started planting pollinator-friendly plants last year: swamp milkweed (Asclepias incarnata), native bee balm (Monarda fistulosa), gayfeather (Liatris spicata), coneflower (Echinacea angustifolia), purple dome asters, and others. Early spring flowers include pigsqueak (Bergenia cordifolia), lily of the valley (Corvallis), beard tongue (Penstemon) and big root geranium (Geranium maculatum). This spring, I added elderberry, anise hyssop (Agastache), more bee balm, cherry tomatoes, and saw the milkweed had spread.

The Smart Snacks garden is successful. A variety of bees - native, bumble, honey - as well as P1250883.JPGsoldier beetles, monarchs, dragon flies, and moths come to roost and "snack" on nectar-rich plants and pollen. I, too, snack a bit on mints and cherry tomatoes, as I pass by. The best surprise were six monarch larvae on the swamp milkweed! I look forward to expanding my Smart Snacks garden annually into nearby beds.

For information on Smart Snacks gardens and planting for pollinators:
MN Landscape Arboretum: Smart Snacks Garden

U of M Bee Lab - Plants for Bees

MDA: Pollinators and their habitats

U of M Healthy Foods, Healthy Lives Institute

Identifying Low-Maintenance Hydrangeas

If you drove or walked the three-mile drive at the Minnesota Landscape Arboretum during late summer or fall in 2013, chances are you stopped for a visit at the Earth-Kind® hydrangea trial. Planted in the fall of 2010, this planting exploded with growth and bloom last year and it was hard to resist stopping for a walk through the beds.

K Zuzek, UMN Extension

Photo 1: Locations of the 5 Earth-Kind Hydrangea trials

The hydrangea planting at the arboretum is one of five Earth-Kind® plantings in the Upper Midwest (Photo 1) that are being used to provide information on the performance of 24 hydrangeas being grown under low input maintenance conditions. The Earth-Kind® program was started in the early 1990's by Dr. Steven George at Texas Agrilife Extension Service to promote environmentally responsible landscape management practices that address diminishing water resources, the overuse and misuse of fertilizers and pesticides, and poor soil health that can diminish plant health. Earth-Kind® landscape practices include minimizing irrigation, providing fertility and improving soil health through the use of compost and organic mulches rather than fertilizers, the reduced use of pesticides, and the identification of genetically strong cultivars and species that will perform well under these low input conditions. The hydrangea trial sites are being used both to identify these strong cultivars and as outdoor classrooms to educate the public on environmentally friendly landscape management.

K Zuzek, UMN Extension

Photo 2: Plot preparation at the MLA

Cultivar trial establishment involves creating 4 blocks (planting beds) at each trial site. Each of the 24 cultivars being trialed is planted once in each of the 4 blocks in a randomized design. This means that 4 plants of each cultivar are planted at each site and their location is different within each of the 4 blocks. Four plants at each of the 5 sites provide us with 20 plants of each cultivar to focus our evaluation efforts on. This replication and randomization gives us statistically strong evaluation data to draw conclusions from. Plot establishment includes eliminating native vegetation (this is the one of the few times an herbicide is used) (Photo 2), incorporating 3" of compost into the native soil, planting, and applying 3" of organic mulch (usually wood chips) (Photo 3). Plants receive consistent irrigation as they establish during year 1.

K Zuzek, UMN Extension

Photo 3: Wood chipping during plot establishment

During years 2-4, irrigation is minimized and watering occurs only if plants wilt during periods of severe drought. Throughout the 4 year study, herbicides are applied only to control invasive weeds such as Canadian thistle if they appear in the plots. The 3" mulch layer minimizes weed establishment and weeds that do appear in the plots are removed by hand weeding. No fertilizers are applied. Organic mulch is reapplied as needed to maintain a 3" depth.

K Zuzek, UMN Extension

Photo 4: MLA plots in year 2 (July 2012)

During years 2-4, evaluation data is collected monthly on the 96 plants at each site. Data is collected on floral and foliar quality, plant size and habit, tolerance to environmental stresses (cold hardiness, drought tolerance, high soil pH, etc.), disease and insect tolerance, and the ability to perform well across a wide variety of soil conditions. Superior hydrangea cultivars that perform well across years and trial sites will be designated as Earth-Kind plants for their region so that gardeners and horticultural professionals know that these cultivars perform well with basic plant care.

K Zuzek, UMN Extension

Photo 5: MLA plots in year 3 (July 2013)

Twenty-four hydrangea cultivars were planted in the trial. Fourteen of the cultivars are panicle hydrangeas (Hydrangea paniculata) and include First Editions® Great Star, First Editions® Tickled Pink®, First Editions® Vanilla Strawberry™, First Editions® White Diamonds®, 'Grandiflora' (also known as PeeGee), 'Limelight', 'Little Lamb', Little Lime™, 'PeeGee Compact', 'Pink Diamond', Pinky Winky™, Quick Fire®, 'Tardiva', and 'Unique'. Seven of the cultivars are smooth hydrangeas (H. arborescens) and include 'Anabelle', 'Bounty', Endless Summer® Bella Anna®, 'Hayes Starburst', Incrediball®, Invincebelle® Spirit and White Dome®. The remaining three cultivars are bigleaf hydrangeas (H. macrophylla) and include Endless Summer® Blushing Bride, Endless Summer® The Original, and Endless Summer® Twist-n-Shout®.

The Benefits of Earth-Kind®
Low input gardening and the identification of plant cultivars that thrive with minimal maintenance benefit gardeners and the environment. The use of genetically strong and well-adapted plants makes it much easier and more enjoyable for gardeners and landscapers to create and maintain beautiful landscapes. There is also a large reduction in labor and the cost of maintenance. Few plants need replacing if adapted and pest-tolerant cultivars are selected for use in a landscape. The use of these tolerant cultivars minimizes the amount of irrigation needed and the use of pesticides. Replenishing organic mulches can be labor intensive but the benefits to gardeners and plants far outweigh the added labor. Mulch provides weed control, reduces the need for irrigation by decreasing evaporation of water from soil, and buffers soil temperature to protect roots during the intense cold of winter and the heat of the growing season. As it decomposes mulch improves soil structure and creates healthier root environments for garden plants: nutrient- and water-holding capacity increase in sandy soils and soil porosity, water infiltration and drainage, oxygen levels, and root penetration improve in heavier clay soils. The health and appearance of plants improves as soil quality improves. Improved soil texture also goes a long way towards making the job of hand weeding a much easier task for gardeners.

As individuals, the impact of our landscape management practices on the environment may be very small but collectively we have an enormous and sometimes a negative impact. As we change our gardening practices, we can reduce or eliminate these negative impacts. Fertilizers and pesticides have the potential to decrease water quality if they move over impervious surfaces such as driveways and sidewalks and into our streams, rivers and lakes through storm sewer systems. As the use of these chemicals is reduced, so is the potential for them to reach the water bodies that we treasure so much in Minnesota. The use of water-wise practices such as drip irrigation and the selection of drought-tolerant plants help to conserve water resources in a time when climate change is creating longer and more frequent periods of drought that put additional demands on these diminishing water resources. The use of organic mulches improves soil quality and reduces the amount of yard waste entering landfills.

The benefits of low input landscape management practices have been documented in Texas where the Earth-Kind® program has been in existence for over 20 years. In gardens or communities where Earth-Kind® landscape management practices are practiced, there have been 50-70% water savings, a 98% reduction in the use of pesticides, and a 20% reduction of yard waste entering landfills. In Addison, TX where the parks & recreation department uses Earth-Kind® management, there was a 50% reduction in labor costs due to the reduced need for irrigation, weeding, fertilizers and pesticides, and replanting. The department saw a 70% reduction in water usage and lost the dubious honor of being the town's largest water consumer.

The effectiveness of the Earth-Kind® plant evaluation effort can also be seen in Texas. To date, 23 roses have been designated as Earth-Kind roses for the southern United States. These plants have high tolerances to pests and perform beautifully under harsh summer temperatures and drought conditions such as those seen in 2011 when Dallas set records for the most 100 degree days, highest daytime and night temperatures, and drought (3.6" of rainfall from March to August instead of the average 17").

Thanks for listening! P1250793.JPG

We aren't always able to answer everyone's text'd questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources.

Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

From Dave in South St Paul:
My tomatoes are flat and rotting on the bottom. What causes this? I water at the base and they are in containers.

Answer: This is a condition called "blossom end-rot". It is the result of calcium deficiency in the developing tomato fruit. This does not necessarily mean there is not enough calcium in the soil though - just that plant is unable to acquire it. This is due to environmental conditions such as fluctuations in soil moisture, heavy applications of nitrogen fertilizer, and injury roots.
Read more ...

Question: Why do my squash and cucumbers always cross-pollinate? They are planted 15 feet apart.
It's typical for Curcubits varieties to cross-pollinate. They are in the same genus, they bloom at the same time and they are both pollinated by (usually) bees. Successful pollination produces a seed(s) and the tissue that surrounds it. It's important to note that this year's pollination will produce the seeds for next year's plants provided you save seed. Therefore, if you are planting seeds from a seed packet you purchased or transplants you purchased from a greenhouse, you should get the kind of squash / cucumber on the labeled. It's next year you  may get a variation on the original seed due to cross-pollination.

Question: I have had some success wintering begonias. Do you have suggestions for more success?

Answer: When you bring plants indoors for the winter, take this opportunity check them thoroughly for insects and insect eggs especially under the leaves. Wipe / rinse leaves, remove any signs of insects like webbing, and remove/dispose of dead leaves and flowers both on the plant and on the soil surface. Transplant into a clean pot with new potting soil. If the plants are large, consider cutting the plants back about 1/3 to just above a leaf node (a node is the point where a leave grows from a stem). Water and place in a sunny window. Begonias do not do well when over-watered, so check the soil about 2" down with your fingers before watering (recommended for all houseplants). and water if dry. You may find plants that are brought in from the out of doors will drop leaves initially. Remove the dropped leaves and continue watering as usual. Wait to fertilize when new growth appears with a complete fertilizer - 10-10-10 (N-P-K) or similar - at half the recommended strength.

Question: We want to seed about an acre. What type of seed do we use that takes, grows fast, and makes a great grass?

Answer: Choose a grass variety based on your conditions (the amount of light, soil type, moisture level) and based on the kind of activities for which you plan on using the area (sports, low-traffic, play area). Here is a good resource: Turfgrass Selection for Sustainable Lawns

You'll see from the Upper Midwest Home Lawn Care for Cool Season Grasses calendar that mid-August to mid-September is the optimal time for seeding your lawn. Seeding in this time period provides cooler temperatures, encourages germination, and enables the grass seed to form healthy roots before gradually going dormant for winter.

Question: Plum tree loaded with fruit. When is the best time to prune so the branches are not on the ground?

Answer: A good problem to have! Support the plum branches with sawhorses, PVC pipe, or other sturdy braces. Harvest the fruit as soon as it is ripe to reduce attracting pests like yellow jackets or birds damaging fruit. Then prune the tree when it is dormant - March or early April in Minnesota. See Stone Fruits for Minnesota Gardens for specifics on pruning including diagrams. Extension also has a great publication on pest management for stone fruits here.

Question: My Hydrangea doesn't have any flowers on it yet. Do they bloom every year?

Answer: Hydrangeas that are hardy in Minnesota typically bloom every year. Factors that can influence blooming include:

  • whether the plant is hardy in your zone (example: the Hydrangeas from a florist are not typically hardy for our landscapes);
  • weather issues such as late frosts that affect flower buds;
  • the amount of light the plant receives;
  • fertilization;
  • pruning techniques - some people prune off flower buds unknowingly;
  • whether the plant blooms on old or new wood;
  • animal damage such as deer browsing.

Some Hydrangeas are just starting to bloom now too. Without knowing the kind of hydrangea and the care you have given it, it's hard to say why your particular plant isn't blooming. However, we have had numerous people ask why their Endless Summer Hydrangea looks healthy, but doesn't bloom or bloom well.

From Paul Cherba: I am getting powdery mildew on my lilacs. Or something white. What can I do about that?

Answer: Common lilacs often get powdery mildew at this time of year due to higher humidity levels. It's typically more cosmetic than detrimental to plant health, and the spores are common and windblown, so there isn't a way to avoid it now or any action to take. Fungicides are available to spray. They are most effective if used at the onset of the mildew (see publication reference below).

Choosing plants that are resistant to pests like powdery mildew is the best option for minimizing its affect. Spacing plants according the their mature size and pruning to increase light and air circulation through the canopy / shrub also is helpful. Prune lilacs within two weeks of flowering before they set flowers buds for next year. Watering at the base of the plant will help keep plant leaves free of water droplets that can hold bacterial and fungal spores. More on powdery mildew on lilacs.

Question: My impatiens were beautiful and now they have been snipped of their leaves and flowers with only stalks left.

Answer: If the leaves have been eaten (they are not lying on the ground), then I would say it was rabbit damage or deer damage. If the leaves have dried up and fallen off the plant, you may have a disease such as impatiens downy mildew. This is a relatively new pest for Minnesota gardeners that affects shade-loving impatiens Impatiens walleriana (not New Guinea impatiens). White fluffy growth forms on the underside of the impatiens leaves. There is no cure and the plants should be removed. Avoid replanting Impatiens walleriana in the same bed. Read more here.

Question: I plan on planting an Autumn Blaze maple where my hackberry once was. When is the best time to plant this?

Answer: Planting a diversity of trees is really important. Trees provide shade, habitat for birds, animals and beneficial insects, and create canopies that cool our landscapes and homes - not mention being beautiful and valuable additions to our landscapes. Late summer / early fall is a good time for planting trees, so right now! Cooler temperatures mean less heat stress on the new trees. Here's a helpful Extension publication on planting trees. Good luck!

Repairing Lawns Following Flooding

The month of June was a wet one. Many homeowners, grounds managers, and golf course superintendents are finally starting to see some of the flood waters recede, although standing water is still covering many of our landscapes. The University of Minnesota's Climatology Working Group is calling June of 2014 the wettest month on record. In the Twin Cities we saw 11.36 inches of rain for the month, almost 7 inches above average and falling just short of the 11.67 inch record set in 1874.

We are starting to see a wide range of damage to lawns and turfgrass throughout the state. In situations where standing water was present for greater than 7-10 days, the turf is almost certainly dead and will need to be repaired. Turfgrass covered for less time has a greater chance of recovery, but every situation is different. Unfortunately, there is not good information regarding how long turfgrass can survive under standing water because there are so many potential mechanisms of damage. These mechanisms can be separated into 2 groups: primary damage from waterlogging and secondary damage after the water has gone.

Primary damage includes such factors as water temperature and water depth. Water temperature will probably be the most important factor determining survival, with turfgrass death occurring in only a few days when water temperatures are 80 degrees F and higher (note: we did not see water temperatures this high during recent floods, unless it was very shallow and stagnant). When water temperatures are lower the turf can still die, with lack of oxygen being the primary culprit. If the turf is completely submerged, this will be a worse case than if some of the leaves and crowns are exposed.

Secondary damage might be associated with sediment buildup, fungal diseases, moss and algae, and weed infestation. While we have very little control over the primary mechanisms causing damage, now is the time to start thinking about how to reduce damage that could be caused by the secondary mechanisms. The primary disease you could expect to occur after flooding is pythium blight. Look for circular or irregular patterns of dead turf inside of healthy turf areas. For more information on pythium blight, follow this link to a fact sheet from Purdue University Extension: Pythium Blight. Remember that plant disease samples can be submitted to the University of Minnesota Plant Disease Clinic for correct identification and control recommendations. If you have confirmed that you lawn is infected with pythium or other diseases, I recommend contacting a lawn care contractor to carry out the control measures.

To this point I've been recommending that homeowners be patient and assess the damage as it presents itself. Turf that appears to be dead following the receding of flood waters should be monitored for several days; if no green tissue appears within 7-10 days, you can assume it is dead and should start forming a renovation plan. In many cases, you might be surprised with the amount of turf that recovers when the conditions are right. In situations where sediment or debris buildup has occurred, you will want to act fast to remove it. The previous Turfgrass Extension Educator, Bob Mugaas, wrote a great article addressing repair of areas where sediment has built up in the 2010 edition of the Yard and Garden News. That article can be found here: Repairing Flooded Lawns

Timing of repair can be difficult. The cool-season grasses that we grow in Minnesota do not establish well in the middle of the summer due to the high heat and diseases that may occur. If at all possible, I recommend waiting to seed until temperatures cool in the early fall around mid- to late-August. Fall seeded lawns will have a much better chance of a successful establishment. With that being said, recovery in the short term could be promoted by aerating your soil once it is dry and/or applying light rates of nitrogen based fertilizer.

Choice of turfgrass seed can be very important. If flooding is a common occurrence on your lawn, I would recommend Kentucky bluegrass over perennial ryegrass or fine fescues. The University of Minnesota Extension has numerous resources to help you in repair process. Please follow these links for more information:

Purchasing Turfgrass Seed

Finding the Right Grass Seed

Renovating an Existing Lawn

Lawn Diseases

Weed Control

Finally, feel free to reach out if we can be of help. You can contact me directly at: or 763-767-3518

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: Native bee nesting site on U of MN St. Paul campus

Karl Foord

Photo 2: Native bee leaving nest to forage - nest hole lower right of photo

Karl Foord

Photo 3: Native bee nesting site on Como Ave. St. Paul

Karl Foord

Photo 4: Native bee navigating grass in front of nesting site

Karl Foord

Photo 5: Native bee approaching nest with pollen load

Karl Foord

Photo 6: Native bee nesting site - Purgatory Park, Minnetonka

Karl Foord

Photo 7: Native bees at hole entrances

Karl Foord

Photo 8: Bauer Berry Farm - Champlin, MN; Note each flag represents a single nest

Karl Foord

Photo 9: Nest entrance hole Bauer Berry Farm - Champlin, MN

One of the projects I am engaged in this summer is the identification and location of the nests of native bees. My partner in this effort is Heather Holm, who is the author of a recently published book entitled, "Pollinators of Native Plants". With additional help from Joel Gardner, a bee biologist and graduate student at the University of Minnesota, and Colleen Satyshur, the research coordinator at the Cedar Creek Ecosystem Science Reserve, we have been able to identify a half dozen different nesting sites of ground nesting native bees. These sites have included areas on: 1) the University of Minnesota campus (Photos 1 & 2), 2) the front of an apartment complex on Como Avenue in St. Paul (Photos 3, 4 & 5) , 3) Purgatory Park, Minnetonka (Photo 6 & 7), 4) a pick-your-own blueberry farm in Champlin Minnesota (Photo 8 & 9), 5) a pick-your-own blueberry farm in Maiden Rock, Wisconsin, and 6) a residence in Chaska.

These sites had several features in common. There was a degree of exposed soil and the areas were mostly untended e.g. ignored or left alone. The fact that these areas are undisturbed by human activity is a critical feature. However, this also means that the areas might not meet the standards of tidiness and neatness often embraced by most urban and suburban neighborhoods.

My upbringing left me with the impression that areas with exposed dirt and perhaps a few weeds were the sign of a slovenly, lazy person. One who did not care enough about their own property to maintain the unspoken but expected standard of tidiness. One key aspect of this standard seems to be a weedless dark green lawn.

The lawn is an English invention indicating aristocratic status. In essence a demonstration that the owner could afford to keep land not being used for buildings or food production.

Wealthy families in America began mimicking such English landscaping styles in the late 1700's. The first lawnmowers were invented in the 1830s in England. The subsequent improvement of these machines permitted middle-class families to imitate aristocratic landscapes and grow finely trimmed lawns in their back gardens.

Jump to the 20th century and behold the increased value of a home through landscaping and its most prominent feature - the well manicured lawn. Maintaining such a lawn may require fertilizers, pesticides, and gasoline powered mowing and maintenance equipment as well as water, depending on location.

The University of Minnesota Turf program is searching for ways to reduce the environmental impact of lawns through drought-tolerant, slower growing species as just one of their approaches.

It was the interest in native bees and their nesting sites that has had me reconsider the negative associations associated with some open ground and untidy areas. I now consider such areas to be an important and purposeful part of my landscape, as it provides nesting sites for native bees.

For what used to be an eyesore, is now a place of beauty when occupied by our fascinating native pollinators.

Perhaps it is time to reconsider lawns in terms of their benefits and ecological impacts.

Two Early Flowering Plants for Bees

Karl Foord, Extension Educator - Horticulture

Karl Foord

Photo 1: Andrenid bee approaching Golden Alexander's flower

Karl Foord

Photo 2: Andrenid bee on Golden Alexander's flower

Karl Foord

Photo 3: Two different Andrenid species on Golden Alexander's

Karl Foord

Photo 4: Bombus griseocollis on Blue False Indigo

Karl Foord

Photo 5: Bombus griseocollis on Baptisia australis

Karl Foord

Photo 6: Brown-belted Bumble Bee queen on Blue False Indigo

One of the keys to have a great pollinator garden is to have different types of flowers available for the pollinators at different times of the year. Two early flowering favorites of mine are Golden Alexanders (Zizia aurea) and Blue False Indigo (Baptisia australis).

Golden Alexander's flowers are shallow and easily accessed by small bees with short tongues such as the Mining Bees (Andrenid spp.) shown in photos 1 - 3.

Blue False Indigo flowers are much more difficult to access by small bees but are easily accessed and preferred by bumble bees. The bee in photos 4 - 6 is a Brown-belted Bumble Bee queen (Bombus griseocollis).

Damaged Lawns: Steps to Bringing Some Life Back

Sam Bauer, UMN Extension- Turfgrass Science
Spring Damage
The grass-growing season is in full swing, and for some of you this means repairing turfgrass areas that were impacted by winter injury. By now, it should be apparent which areas of your lawn were damaged (but not killed) from winter stresses and which areas will not recover from winter injury. Plants that are slowly recovering, suffered damage only to the leaves and are able to produce new leaves during the spring. Practices such as removing dead leaf tissue and fertilizing will help expedite the recovery of these areas. In contrast, plants that are dead suffered damage to the crown tissue (survival organ of turfgrasses) and will need to be renovated and repaired. The goal of this post is to provide you with information on the different types of winter stresses that effect turfgrass plants and the cultural practices that can be used to minimize winter injury. In addition, a step-by-step outline of the recovery/renovation process is provided.

Repairing dead turfgrass on a yearly basis can be both time and labor intensive and is an unnecessary added expense. Therefore, one of the first steps to minimizing winter injury is to identify the primary cause of damage. In Minnesota, damage detected in the spring may be attributed to several different stresses that the turfgrass is exposed to during winter months. Specifically, there are five main stresses associated with low temperatures and each has the potential to cause damage and/or death of your lawn. Crown hydration is associated with elevated temperatures (above freezing) and results in an increase in water content of the turfgrass plant. This can be lethal if hydrated tissues are then re-exposed to freezing temperatures causing ice crystals to rupture cells in the leaves and crown. Desiccation causes severe dehydration of plant tissues due to lack of snow cover or inadequate moisture and is generally a problem on elevated areas exposed to wind. Prolonged ice cover can also be damaging to lawns by creating an impermeable layer above the turf resulting in a depletion of oxygen and a build up of gasses that are toxic to lawn grasses. Additionally, grasses can die simply from exposure to low temperatures; however, damage associated with temperatures at or below freezing is minor during winters with adequate snow cover. Finally, snow molds are a common occurrence in Minnesota and winter damage associated with these diseases occur every year. For more information on snow molds, visit this article by Michelle Grabowski: Altogether, these stresses can occur individually or as a complex to cause damage that potentially could be lethal to the turfgrass in your lawn.

Along with the five mechanisms causing winter injury to lawns, there are also many other abiotic stresses that occur throughout the spring period. Salt loading from the use of de-icing salts commonly causes damage to turf along roadsides, sidewalks, and driveways. Primarily, these salts cause severe desiccation of leaf and crown tissue and ultimately result in death of the turfgrass plant. By the time the salts are leached through the soil profile with spring rains, most of the damage has been done. In addition to deicing salts, dog urine spots can kill grass from the high salt content and can cause excessive growth due to nitrogen in the urine. Mechanical damage caused by snowplows, mowing too early, and power raking early in the season can also result in areas of turfgrass that need to be repaired in the spring.

Preventing/minimizing winter injury is a yearlong process and involves knowing your lawn and carefully considering the maintenance practices utilized to maintain the turfgrass. For example, in areas that frequently accumulate standing water, core aeration will help with water infiltration as snow melts in response to warming temperatures. Overall, this will reduce the potential for crown hydration and ice crystal formation along with helping to prevent the establishment of an impermeable ice layer. An additional consideration is fertility, specifically associated with the application of nitrogen. Snow molds are more common on lush, succulent turf, and a heavy application of nitrogen in the fall could promote damage caused by snow molds. In addition, succulent turf is more prone to injury attributed to exposure to temperatures at or below freezing. Keep in mind that as summer transitions into fall keep the cultural practices implemented have a direct impact on the survival of turfgrass plants throughout the winter and into spring.

Steps for Recovery
Providing the right conditions for your lawn to thrive is the most important component of a good recovery program. While it's up to Mother Nature to supply the main ingredients, maintenance practices should focus on creating the optimum growing environment for the turfgrass species in your lawn. The following steps outline the processes required for repairing damaged/dead areas of your lawn and also cover factors to consider for managing the overall health of turfgrasses.

1. Choose a mixture of grass to be planted. This is also where the choice of seeding or sodding comes into play. Sod is good for situations where you desire instant turf cover and quick stabilization. With sod, your species and variety options will be limited because not all grasses form an acceptable sod. Kentucky bluegrass is the standard for sod in Minnesota due to its high aesthetic quality and extensive rhizomes that aid in holding the sod together. Recently, fine fescues have been included in specific sod mixtures for the use on roadsides because of their good performance in high salt environments. This sod also makes a great low maintenance option for home lawns. A list of suppliers of this sod can be found here:
Sod must be watered daily (more frequently in heat and drought) for the initial week, in the absence of rain. Watering should be focused on wetting the sod and the underlying soil; however, after roots emerge from the sod, irrigation should be less frequent in order to encourage further root growth. Seed should generally be watered multiple times a day lightly. The trick here is to keep the surface moist during the germination period. Excessively wet conditions will cause deterioration of seed and seedlings, and encourage turf diseases and weeds. Remember to avoid watering when precipitation is sufficient.
For help finding the right grass species and seed, visit these resources:

Turfgrasses for Minnesota lawns

Finding the right grass seed

Purchasing turfgrass seed

2. Prepare the area for seeding or sodding. No matter which method of establishment you've chosen, preparation of the surface will generally be the same. The surface should be smooth, weed-free, and not compacted. If seeding into existing grasses, a slit-seeder or vertical mower can be beneficial to ensure good seed to soil contact, but be sure not to plant the seeds too deep (1/4" would be the maximum depth to plant seed). In addition, aeration followed by seeding can also be very successful. For sod, removing existing vegetation and smoothing the surface should prepare areas. The thickness of sod is generally around 1.5 to 2" and this should be accounted for when preparing an area to be sodded. In addition, soil tests can be conducted at this time to determine nutrient status and unfavorable conditions in your soil. Soil samples can be submitted to the U of M Soil Testing Laboratory

3. Apply fertilizer and/or soil amendments as determined by your soil test. If you don't have a soil test, a general recommendation for establishment of seed or sod is to apply a starter fertilizer (high phosphorus, ex. 10-20-10) at a rate of 1lb phosphorus per 1000ft.sq. If the fertilizer in the example is chosen, this would also supply 0.5lb of both nitrogen and potassium. If applying fertilizer only, you have the option to put it down before or after seeding, or above or below sod.

4. Plant seeding or install sod. For seed, be sure to check the seed label for the proper rate. Kentucky bluegrass should be seeded at 1.5 to 2lb per 1000ft.sq, whereas fine fescues should be seeded at 4 to 5lb. Seed can be applied by hand, or preferably with a drop-type spreader. Rake the seed lightly into the soil surface. If sodding, take care to tightly pull the sod seams together. The seams of sod rolls should be staggered in a brick like pattern to avoid channels for water movement. And sod should be installed perpendicular to slopes.

5. TLC. This last step is one of the most important for successful establishment of your new grass. Particularly, moisture content of the surface and soil will be a major determining factor on the recovery rate of those damaged or dead areas. The amount of water necessary for turfgrass establishment varies greatly and depends on factors such as soil type, air temperature, and whether the area has been seeded or sodded. Consequently, monitoring the newly renovated area(s) is key to ensuring that irrigation isn't being over or under applied.

We see sod die and seedlings lost from both over- and under-watering. Unfortunately, there's no general formula for success from a watering standpoint. For seed, the surface should be maintained moist like a sponge. During hot and dry periods this might mean watering 3-4 times per day with 0.05 to 0.10" each time. As seedlings emerge, the amount and frequency of watering can be reduced and this typically occurs approximately 1 to 2 weeks after seeding. For sod, irrigation should be frequent during the first couple of days; however, this should be reduced in order to encourage rooting into the underlying soil. Sodded lawns will benefit greatly from several core aerations in the initial years.

A follow-up fertilizer application can be applied around 2 weeks after seeding to encourage establishment and density. Sod can be mown rather quickly, possibly even a week after being installed if using a hand-operated mower. Larger mowers can damage sod if they are used too soon; before operating large equipment on sod, check to be sure the sod is rooted into the soil. Seeded areas can be cut just as the grass starts to grow beyond the desired height of cut, generally 2.5 to 3" for lawns. Getting seeded areas mown soon will help to reduce weeds and encourage density in the turf, be sure to use lightweight equipment.

By using these five steps you should be able to recover even some of the worst lawn situations. Remember, choose the right plant for the right place and maintain balanced moisture. These are the most important factors throughout the recovery process.

Where's the Redbud Bloom?

Over the past 30 years, Minnesotans have enjoyed many mild winters. But the winter of 2013-2014 was a return to the winters of yore. In many parts of the state, the past winter was the coldest in either 35 or 78 years and it is a winter that will be remembered for long persistent periods of very cold temperatures. The persistent cold allowed deeper than normal frost penetration in soils even though snowfall was heavy and just as persistent as the cold temperatures. No matter what statistics you look at - lowest temperatures recorded in the state, average monthly temperature, number of days Minnesota reported the coldest temperature in the nation, amount and persistence of snow cover, soil frost depth, windchill conditions, number of nights with 0 degrees or lower - they all add up to one long, cold, snowy, difficult-to-live-through winter.
The past winter also took its toll on trees and shrubs. Winter burn on evergreens and salt damage on roadside white pines were severe. With the arrival of spring, cold injury to plants that are marginally hardy in Minnesota showed up. Vegetative damage can be seen in most of the repeat-blooming shrub roses whose canes died back to the ground. These plants are now busy sending up new canes from their crowns. Because repeat-blooming roses produce flower buds on this year's canes, these plants will still be able to bloom throughout the summer.

K. Zuzek, UMN Extension

Photo 1: Eastern redbud flower

D. Hansen, MN Ag. Exp. Stn.

Photo 2: Eastern redbud without flower bud winter injury

Winter injury to flower buds occurred among other plant species. Among marginally hardy plants that have been introduced to Minnesota from warmer climates, flower buds are often less hardy than vegetative parts such as leaf buds and stems. An example of this type of injury from the past winter is being seen on eastern redbud (Cercis canadensis). Eastern redbuds are small trees with lavender pink pea-like flowers that open to cover tree canopies in May before heart-shaped leaves expand. Flower buds formed during the growing season of 2013 should have provided us with beautiful bloom this spring. Some redbuds in the heart of the Minneapolis/St. Paul did bloom. But thanks to our low winter temperatures the more common scenario, especially in suburbs surrounding the Twin Cities and in colder outstate locations, was flower bud mortality and lack of bloom.

K. Zuzek, UMN Extension

Photo 3: Eastern redbud with flower bud winter injury

Redbuds are not native to Minnesota. Their native range extends throughout much of the eastern half of North America. In the Midwest, the range extends only as far north as southern portions of Iowa, Wisconsin, and Nebraska. The species is considered hardy to Zone 5 where average minimum temperatures fall between -10 degrees F and -20 degrees F, meaning it lacks the cold hardiness needed to survive and perform well in almost all of Minnesota. But decades ago a large number of redbud seedlings were planted at the University of Minnesota Landscape Arboretum and Horticultural Research Center. Some of these proved hardy enough for use in Minnesota landscapes. Over the last 20 years, seed from these trees have been collected each year and plants grown from this seed are sold as the Minnesota strain of redbud. Even with the improved hardiness of the Minnesota strain, redbud bloom is not 100% reliable and in the most severe of winters (such as the winter of 2013-14) flower buds are killed by low winter temperatures. Cold injury to eastern redbud flower buds used to be more common so that lack of bloom occurred every 4 or 5 years. With winter temperatures trending warmer over the last several decades, redbud bloom has been so much more consistent that this year's lack of bloom may seem unusual to all but the oldest few generations of Minnesota gardeners.

Mary Meyer, Extension Horticulturist

Mary Meyer

Figure 1: Ostrich fern background, maidenhair fern foreground

Mary Meyer

Figure 2: Gooseneck loosestrife has almost comical flowers

Mary Meyer

Figure 3: Northern seaoats' flowers are pendulous and easily self-seed

Mary Meyer

Figure 4: From left 'Northwind', Warrior', 'Thundercloud', and Cloud 9' Switchgrass

My backyard is at the bottom of a slope that easily floods when we have a 'rain event' of a few inches. The water can even stand in this area for 12-24 hours - fatal for some plants. To make matters worse, the soil is sandy, so when rain is scarce, the soil is bone dry- again fatal again for some plants. I have three tough perennials that have lived well in this area, all of which are shade tolerant: ostrich fern, Canada anemone and gooseneck loosestrife. All three of these plants have aggressive rhizomes that have helped them to live in this difficult site. I believe all of these plants will grow well in USDA Plant Hardiness Zone 3. However, northern seaoats will only live as an annual, but it will self-sow enough to come back each year.

Ostrich fern (Matteuccia struthiopteris) is a tough native fern (photo 1). Some people may think the ostrich fern is too tough, with its rhizomes and substantial root system. I love the soft feathery fronds and the fact that it will tolerate standing water and survive droughts. In the driest years, the plants are shorter, the rhizomes do not spread, and the plants die back prematurely. In wet years, it begins very aggressively and grows into the adjacent lawn. I transplant it to other shady locations where I want it to grow. The fertile fronds are stiff, much shorter and still standing in the spring when I break them off and push them into the ground as a standing border for the sedge planting that is up the hill under the box elder. This acts as a border signaling my husband where to mow the lawn and not the sedges.

Canada anemone (Anemone canadensis) is another tough native that easily can be too aggressive due to creeping rhizomes. However, the tough conditions of this site keep it in bounds. It is a sea of 1-2 foot tall white flowers in the spring. The foliage is often confused with wild geraniums, but the single white flowers have a cluster of yellow stamens, typical of the buttercup family, and lack the beak-like style of geraniums. Canada anemone foliage makes a thick ground cover that competes well with other weeds, even buckthorn seedlings!

Gooseneck loosestrife (Lysimachia clethroides) is a 2-3 foot tall perennial native to China (photo 2). I am adding it anyway because it has lived in this tough situation as few other plants would. It also has aggressive rhizomes. In dry years the plants are short and do not spread at all, while In wet years it is tall and robust. I step on it to keep it in bounds as I go to the compost pile, or edge it with the lawn mower. The gooseneck flowers are fun to look at and a delight in floral arrangements. It is one plant that blooms regardless of weather conditions.

Other plants (grasses are my favorites!) that I could add in this site are:

Wood oats or Northern seaoats (Chasmanthium latiflium) (photo 3) are native to south central U.S. and marginally hardy in zone 4. This grass self-seeds and although one plant may die, another will likely come up on its own. This is a bunch grass, with no rhizomes. It has the best flowers for dried arrangements and will last for years if picked early before the seeds are fully developed. The pendulous flowers are flat and beautiful in the fall when they turn bronze and yellow. This grass is native in wooded areas along river banks and it prefers wet sites where it can grow to 4 feet. In drier sites it may only be 2 feet tall. A newer form 'River Mist' is yellow and white striped, much shorter e.g. 18 inches, and has only lived as an annual for me.

Prairie cordgrass or slough grass (Spartina pectinata) is a larger, 4-6 foot tall, long-leaved grass for wet sites that will tolerate standing water and lakeshores. Native to prairies and often found in roadside ditches, slough grass has creeping rhizomes ideal for binding lakeshores. This grass is large and coarse, good for larger sites. In areas containing only cattails or reed canarygrass, prairie cordgrass can be added to increase diversity. An ornamental form of prairie cordgrass ('Aureomarginata') has yellow stripes on the foliage and creeping rhizomes. Prairie cordgrass prefers full sun conditions, but can grow in light shade.

Native switchgrass (Panicum virgatum) is in almost every roadside ditch across Minnesota. Many ornamental forms are available; we are trialing 17 of these at the Minnesota Landscape Arboretum Grass Collection (Photo 4). Plan to come in September and pick your favorite. The 2014 Perennial Plant of the Year ('Northwind') was selected by the Perennial Plant Association for its 5 foot tall, stiff upright form and olive green foliage. 'Shenandoah' (4' tall) and 'Ruby Ribbons' (2' tall) both have red foliage and flowers. "Cheyenne Sky' is purple and red and grows to 4 feet tall. Most switchgrass plants will tolerate wet soils quite well. They are taller in wet sites and shorter under dry conditions. Switchgrass is a bunch grass and does not have creeping rhizomes, however, it can self-seed readily. Switchgrass prefers full sun conditions and will only tolerate very light shade.

Minnesota's Native Holly

K. Zuzek, UMN Extension

Photo 1: Winterberry, November 11, 2013

Mention holly during the month of December and we all think of cut holly branches adorning homes during Christmas season. But our native holly, called winterberry or Ilex verticillata, is just as ornamental outdoors in our early winter landscapes because of its colorful and abundant fruit (Photo 1).

Winterberry is native throughout the eastern United State (Photo 2) and in Minnesota it is usually found growing in forested wetlands in the eastern half of the state along with larch, willows, and speckled alder. You may also see it growing along lakeshores and ponds or in acidic sandy soils with high water tables.

USDA Natural Resources Conservation Service Plants Database

Photo 2: Native range of Ilex verticillata

Although there are over 400 species of holly (Ilex spp.) worldwide, less than a dozen species are commonly used as landscape plants. Winterberry is one of these species. Approximately 35 cultivars have been selected within the species for fruit color (red, orange, and gold), fruit size and abundance, and compact plant size.

Winterberry cultivars range in size from 4-10 feet in the landscape. Small, inconspicuous flowers are produced from mid-June to early July. Winterberry's dark green foliage provides a beautiful backdrop to the brightly colored fruit that become showy in September. After leaves drop, the fruit will continue to light up a winter garden until birds find and eat it.

Winterberry is an easy plant to grow in light or heavy soils. Because it is native to swampy areas, it does well in wet conditions. It does prefer acidic soils with a pH between 4.5 and 6.5; chlorosis will develop in high pH soils. The other important fact to remember is that winterberry is dioecious, meaning male and female flowers are produced on separate plants. Besides planting a female cultivar that will produce the showy fruit, you must also plant a male plant whose pollen will be produced at the appropriate time to pollinate the flowers on your female cultivar that will later develop into the fruit. Two male cultivars are available at garden centers: the early blooming 'Jim Dandy' and the later blooming 'Southern Gentleman'. Plant labels and garden center staff can help you select the appropriate male cultivar for your fruiting female cultivar.

Summer 2012 Imprelis Update

Kathy Zuzek, UMN Extension Educator, Horticulture

In June, the Office of Indiana State Chemist published the 2012 Imprelis Soil and Vegetation Sampling and Analysis Follow Up Study showing 2011 and 2012 levels of aminocyclopyrachlor, the active ingredient of Imprelis, from 11 sites where Imprelis was applied. The level of aminocyclopyrachlor (ACP) was measured in both soil and vegetation. Soil samples were taken to a depth of 4 inches and were then divided into the top 2" and the bottom 2 inches. Vegetation sampled included dead spruce twigs, willow twigs, and honeylocust twigs and leaves on Imprelis-damaged trees. Levels were widely variable in both 2011 and 2012 across the 11 sites. But on average, ACP levels in the 2012 samples of were 10%, 6%, and 23% of the levels measure in 2011 for the top 2" of soil, the bottom 2" of soil, and the vegetation samples respectively.

What does this information tell us? 1) ACP levels still present in plant tissue are higher than levels in soil. 2) ACP levels are dissipating as expected according to the half-life (the time it takes for the chemical concentration to reduce by one-half) of Imprelis in turf environments. Unfortunately, there is no information available as to what the remaining ACP levels in soil and vegetation mean in terms of continuing damage or a timeframe for safe replanting in Imprelis-applied soils.

Here is what is happening to tree and shrub species on Imprelis-applied sites in MN since the last update :

Remember that the effects of Imprelis on non-target species (the injured pines, spruce, and other species growing near or in turf where Imprelis was applied as a weed killer) are the same as the effects seen on targeted weed species. ACP is a synthetic auxin or plant hormone. When applied to plants, ACP causes undifferentiated cell division and elongation in areas of new plant growth, primarily branch tips and root tips. The undifferentiated cell division and elongation results in downward bending of leaves or needles, stem thickening, severe necrosis (tissue death), stunted new growth, calloused stems and leaf veins, and crinkling, cupping and twisting of leaves, needles and stems.

K. Zuzek

Photo 1: Late bud break on Colorado spruce in July

K. Zuzek

Photo 2: Thickened shoot tips on eastern white pine

Some species like Colorado blue spruce and cottonwood had a delayed bud break and leaf out this year. Bud break on Colorado blue spruce on an Imprelis-applied site I have been observing occurred in July rather than April (Photo 1).

Among highly susceptible species like eastern white pine, Norway spruce, and white spruce that showed bud and shoot tip injury or mortality shortly after Imprelis applications in 2011, behavior is variable. Some trees continued to decline and died. Others broke bud but the new shoot tips are thickened and often have twisted needles or are completely lacking needles (Photo 2). Others are producing adventitious buds and shoots below dead stems in an effort to put on new growth. It will take time to see if these plants can be managed and restored to worthwhile landscape plants.

K. Zuzek

Photo 3: Cupped distorted foliage on honeylocust in 2012

K. Zuzek

Photo 4: Crown dieback in honeylocust

Among deciduous trees and shrubs, leaves produced in 2012 are sometimes still showing distortion, twisting, and cupping due to 2011 Imprelis applications. Honeylocust (Photo 3) and lilacs are good examples of this.

The most recent development on Imprelis-applied sites in Minnesota is on honeylocust. As has been seen in states east of Minnesota, honeylocust seems to be a particularly vulnerable deciduous tree species. Many honeylocust have died. Among those that survived, many have dieback in their crowns this year (Photo 4), a more open canopy due to reduced leaf formation, twisted and distorted foliage, and galls or tumors on the trunk (Photo 5) and throughout the tree canopy (Photo 6).

K. Zuzek

Photo 5: Honeylocust trunk galls

K. Zuzek

Photo 6: Galls in honeylocust canopy

An Imprelis Update

Kathy Zuzek, UMN Extension Educator, Horticulture

The History of Imprelis
In October of 2010, a new broadleaf weed killer by the name of Imprelis became available to turf professionals. Key to DuPont's release of this herbicide was its effectiveness at very low concentrations, its low toxicity to humans and other mammals, and its effectiveness on difficult-to-control turf weeds such as creeping Charlie, wild violets, clover and Canada thistle.

During the spring of 2011, damage to ornamental plants in landscapes where Imprelis had been applied began to appear in the eastern half of the United States including Minnesota. Damage to new growth of plants became visible within a matter of weeks after an Imprelis application and included twisting and/or browning of shoot tips, leaves, and needles (Photo 1).

K. Zuzek

Photo 1: Brown, twisted, & drooping shoot tips from Imprelis applications

As the summer progressed, impacted shoots and their associated leaves, needles, and buds often died on the most susceptible species. In some cases, entire trees or shrubs died. Broadleaf and conifer species of ornamental plants were impacted but conifer species were impacted much more severely. The most seriously impacted species from states east of Minnesota were Norway spruce (Picea abies) and eastern white pine (Pinus strobus) trees. The most seriously impacted species in Minnesota were white spruce (Picea glauca) and eastern white pine, but noticeable damage to Colorado blue spruce (Picea pungens), Norway spruce, Austrian pine (Pinus nigra), red pine (Pinus resinosa), and arborvitae (Thjuja occidentalis) were also common. A wide range of damage was seen among all of these species. Some plants showed little injury throughout the 2011 growing season, others died quickly, and the symptoms on others became more severe as the growing season progressed. The number of plants damaged, the level of damage, and plant mortality was highest among white spruce and eastern white pine in Minnesota.

In August of 2011, sales of Imprelis were stopped but damage to trees and shrubs in landscapes continues to be an issue. DuPont initiated a claims resolution process to compensate customers with damaged or killed plants. The deadline for claims submission was February 1, 2012 and DuPont is now processing claims submissions. Lawsuits have also been filed against DuPont.

How Imprelis Works
Aminocyclopyrachlor is the active ingredient in Imprelis and is classified as a synthetic auxin or growth regulator type of herbicide. Imprelis and other growth regulator herbicides are absorbed by roots and leaves and then move via the xylem & phloem to two of the meristematic regions responsible for new plant growth: shoot tips and root tips. In susceptible plants, growth regulator herbicides produce characteristic twisting and curling of the shoot tips and their foliage and plant mortality often follows. Herbicides are meant to kill and eliminate targeted plants such as weeds. When they impact non-targeted plants such as conifers in the case of Imprelis, problems arise.

Imprelis does not bind well to soil particles and is a very water-soluble compound. It is also a very stable compound in soil. Because it is active over a long period of time in soils and because its low adsorption and high solubility allow it to move downward in soil once applied to turf, it appears that Imprelis was able to reach the root systems of ornamental plants. Absorption of the herbicide occurred through the roots of these plants, followed by movement through the plant to new growth areas, and injury occurred. It is still not known why particular spruce and pine species are so susceptible to Imprelis.

K. Zuzek

Photo 2: Branch with active bud-break


K. Zuzek

Photo 5: Branch with no bud-break

Will Trees Damaged by Imprelis Recover? The answer to this question depends on the severity of damage. Trees that showed minimal damage (such as a small amount of injury at shoot tips in the upper branches of a tree) during the spring of 2011 and had little additional decline during the growing season will probably survive.These trees have active bud-break and are putting on new growth throughout most of their crowns this spring (Photo 2). Most broadleaf trees and shrubs and some of the conifer species that were impacted by Imprelis are in this group. Retaining these trees and shrubs in the landscape will depend on how badly damage impacts their appearance. Care of these plants during the recovery period should include irrigating the plants during dry periods to minimize moisture stress, avoiding over-watering that can cause additional stress, and avoiding fertilization for a minimum of one growing season to avoid excess growth that can compound herbicide injury.

Trees that showed damage last spring (Photo 3), further decline (dieback of shoots, dead needles and buds, yellowing of the tree canopy) during the 2011 growing season and/or the winter of 2011-2012 (Photo 4), and limited or no bud-break throughout the tree crown this spring (Photo 5) will probably continue to decline and then die. Even if these trees do not die, they will be of little or no aesthetic value in the landscape. In Minnesota, the majority of trees in this group are white spruce and eastern white pine.

K. Zuzek

Photo 3: Initial symptoms on white spruce in July, 2011

K. Zuzek

Photo 4: Symptoms on the same white spruce in April, 2012

DuPont's Compensation Plan If you are a property owner with Imprelis-damaged plant materials and you and your lawn care professional are part of the claims resolution process that DuPont enacted, you can access information on the claims process here. Compensation will cover removal and disposal of impacted trees, replacement costs or direct payment for removed trees, care of replacement trees , two-year warranties for all replacement trees and for any other trees impacted by Imprelis over the next two years, maintenance of impacted trees as they recover, and additional compensation for inconveniences associated with Imprelis.

Removal and Disposal of Plant Materials and Soil containing Imprelis
Listed below are some of Dupont's recommendations for the disposal of plant materials and soils containing Imprelis. These recommendations are for individuals who had Imprellis damage to plant materials but are not part of the claims process against DuPont. You can access the full list of recommendations here .

    Disposal Recommendations
  • No tree debris should be left on site.
  • DuPont recommends disposal of tree and excavated soil materials in solid waste landfills that will accept such waste.
  • The Imprelis label prohibits the use of grass clippings for mulch or compost.
  • Under no circumstances should tree material be used for mulch or compost or disposed of in facilities that would turn it into compost or mulch (e.g., recycling).
  • Trees that are cut down may be used for lumber, firewood, or to fuel various wood burning processes if such usage is otherwise consistent with state, regional and local regulations. Open burning is also an alternative if approved under local regulations.
  • If not landfilled, excavated soil should be disposed of in locations where it will not impact any other plantings through direct application or runoff. With the property owner's consent, excavated soil may be used on site as long as it is applied well away from desirable plant root.
Recommendation for planting replacement plants:
  • To address potential effects of Imprelis remaining in the soil, activated charcoal (that serves to deactivate any residual herbicide) should be applied to the backfill soil in accordance with manufacturer's instructions:

  • For liquid applications, apply at a rate of 1 pound of activated charcoal in each gallon of water uniformly to sides and bottom of hole dug for tree planting as well as to the complete root ball of the tree to be planted. Also, spray the burlap covered root ball if burlap is left in place. Thoroughly coat to the point of run-off the surfaces of the hole and the root ball.

    For dry applications, during tree planting, apply activated charcoal at a rate of 7 to 14 lbs/1000 cubic feet of soil and thoroughly mix with the clean soil. Use this soil as the new backfill soil when planting the tree.

  • Excavated soil should not be used as backfill. New soil, of a similar nature as the existing soil, should be used to backfill around the root ball. No fertilizer should be added to the backfilling mixture.

  • The replacement plant should be watered according to nursery recommendations.

  • The property owner should ensure adherence to best management practices consistent with the geographic area in which it is performing this work, taking into account any unique environmental and climate conditions, and any state, regional or local ordinances. Information on selecting, planting, and care of trees in Minnesota can be found here.

Based on the degradation rate of Imprelis in soils and on recommended planting times for Minnesota, a good additional recommendation would be to not plant susceptible species into Imprelis-impacted landscapes until September of 2012.

A Look at the New USDA Hardiness Zone Map

A hardiness zone map (HZM) provides information that gardeners and professional horticulturalists use in determining which herbaceous and woody perennial plants will survive cold temperature in a particular geographic area. Last week the United States Department of Agriculture released a new hardiness zone map to replace the older 1990 version.

As with past maps, the new map:
  • is a visual representation of average annual minimum temperatures across the United States. Data points used to create the map were the lowest daily minimum temperatures recorded at thousands of temperature data stations during each of the years sampled.
  • divides the U.S. into multiple hardiness zones with 10o F differences in average annual minimum temperatures. Zone 1 is the coldest zone (-50o F to -60o F).
  • divides each hardiness zone into "a" & "b" with "a" being the colder half of any zone and "b" the warmer half.

There are changes in the new map and the process that was used to develop it:


    Photo 1: 1990 USDA Hardiness Zone Map

  • The 1990 HZM was based on data from a 12-year period (1976-1990) while the new HZM is based on data from a 30-year period (1976-2005).
  • The data used to create the new map was more complete, and a complex algorithm was used to interpolate between recording stations. Temperature data from more than 8000 temperature data stations belonging to the National Weather Service, the USDA Natural Resources Conservation Service, the USDA Forest Service, the Bureau of Reclamation, and the Bureau of Land Management was used. Average minimum temperatures were then calculated for ½ mile square computer grids for the entire country to create the new hardiness zone map. This was followed by a review process that included climatologists, agricultural meteorologists, and horticultural experts who checked for errors, looked for the source of errors, and corrected errors.


    Photo 2: 2012 USDA Hardiness Zone Map

  • The new map is Geographic Information System-based. This means that the map is more accurate, is interactive (by zip code) to improve user experiences, and has higher resolution that can show smaller areas of zone delineations than before. While the 1990 map was a static image and was not designed for web use, the new map allows users to zoom in to a local area to see the higher temperatures of cities that are heat sinks, the lower temperatures on mountain tops, and the buffering effects of large bodies of water on temperature.

What does the new hardiness zone map show?
In general, the new map shows what we have all been experiencing in recent history: warmer low temperatures during winter. A shift of ½ of a zone was common for much of the country. Closer to home, here is what happened to Minnesota's hardiness zone map:


    Photo 3: 1990 USDA MN Hardiness Zone Map


    Photo 4: 2012 MN Hardiness Zone Map

  • There was a ½ zone shift for much of the state because Minnesota, like the rest of the U.S., has been experiencing warmer annual minimum temperatures during the time period used to create the new HZM.
  • Zone 5a (with average minimum temperatures of -15o to -20o) crept up into the south central portion and the far southeastern corner of Minnesota.
  • Much of the southern ½ of Minnesota that was formerly divided into zones 4a & 4b is now zone 4b (with average minimum temperatures of -20o to -25o).
  • The four pockets of Zone 2b (with average minimum temperatures of -40oto -45o) disappeared from northern Minnesota.
  • The amount of Minnesota that is zone 3a (with average minimum temperatures of -35o to -40o) shrank significantly due to an increasing area of zone 3b (with average minimum temperatures of -30o to -35o).
  • Parts of the far northern shore of Lake Superior that were formerly zones 4b and 4a are now designated as 4a and 3b, meaning they are colder.

What kind of impact should the new hardiness map have on Minnesota gardeners?

  • We can all rest easy knowing that the warmer minimum annual temperatures we have been enjoying over the past years really did happen!
  • Remember that a HZM is created based on average annual minimum temperatures and should only be used as a general guide. By the very definition of average, we know that temperatures lower than the average minimum temperature of the zone you live in will occur. Pick your plants accordingly. Maybe we can broaden the palette of plants we choose to grow in Minnesota a bit, but be cautious and wise in your weighing of risk vs. gain as you trial new plants. Losing an herbaceous perennial or quickly-maturing shrub to winter injury may be of little concern in terms of the time it takes to establish a replacement plant. Losing a slow-growing shrub or a tree that takes decades to grow to mature size creates more pain.
  • Hardiness zone maps are of no help in predicting plant damage or mortality during acclimation and deacclimation. Remember that hardiness is not just about the lowest temperature a plant must survive during a winter. Every year, starting in late summer, perennial plants goes through a multi-month process called acclimation that prepares them for winter survival. In spring dormant plants go through a reverse process called deacclimation that restores their ability to actively grow during the growing season. Plants can be winter-injured or killed by abnormally low temperatures during the months of acclimation and deacclimation too. This is especially true of marginally hardy plants from warmer parts of the country or world that we may try to grow in Minnesota.
  • Hardiness zone maps provide gardeners with one category of plant performance information: winter survival. Good plant performance is not just about winter survival. If the new HZM persuades you to plant cultivars and species new to you, remember that there are other selection categories to consider as you match a plant to your planting site: soil texture, soil moisture, soil pH, light exposure, precipitation, etc.

What's New or What's Good

Kathy Zuzek, UMN Extension Educator, Horticulture

An enormous interest for most gardeners during our long winter is the search for new cultivars that can be added to next year's garden. But is new always good? The answer to that question depends on whether new cultivars have been shown to perform well in Minnesota gardens before their introduction into garden centers. Horticultural professionals should provide customers with the best performing plant selections for Minnesota's difficult climate. But the current trend in horticulture is to move new plants onto the market in the shortest possible time frame, creating a rapid process of both cultivar introduction and elimination in the market.

This creates several problems for gardeners interested in sustainable gardening and in planting cultivars known to have long-term landscape value. New cultivars are now introduced to Minnesota gardeners from breeding and evaluation programs around the world. When new cultivars are rushed to the market, there is often no time for the evaluation of the plant's performance in Upper Midwest gardens prior to introduction. Purchasing and planting new un-trialed cultivars among annuals or herbaceous perennials may be an acceptable risk for gardeners to take. These plants are relatively inexpensive and establish and grow to maturity quickly. It is much riskier in terms of money, labor, and time invested if gardeners purchase and grow un-trialed shrubs and especially trees that take decades to reach maturity.

If newly introduced cultivars are displaced quickly by even newer cultivars, there is also little time to evaluate their long-term potential in the landscape between their introduction and their elimination from nursery catalogs. This sets up a situation where newer cultivars prove to be a good performer in our Minnesota gardens but by the time this fact is recognized, the plant has already been removed from nursery catalogs.

The emphasis on new cultivars may also result in the elimination from the nursery trade of much older cultivars as they are removed to make room for new cultivars in a nursery's production schedule. The introduction of new cultivars that have been shown to be improvements over older cultivars is an exciting event for gardeners, especially for northern gardeners who have a smaller pool of plants to choose from than southern gardeners. But what if older cultivars that have proven their long-term landscape value over decades of time are replaced with un-trialed cultivars that fall short of the mark?

As wise gardeners, we can help solve these problems by asking "What's good?" rather than "What's new?" Finding information on plant performance in Minnesota or the Upper Midwest can be a tough go though. Here are some suggestions:

Take advantage of the information available from plant evaluation programs. Plant evaluation programs for the Upper Midwest are few and far between but here are a few examples:

  • The Chicago Botanic Garden has been home to the Plant Evaluation Program for 28 years.

    Kathy Zuzek

    Photo 1: Plant Evaluation Notes

    The goal of this program is to determine, through scientific evaluation, which annuals, perennials, vines, shrubs, and trees are superior for gardens in the Upper Midwest. Information on the program and the 35 Plant Evaluation Notes published to date can be found here.

  • The All-America Selections program was founded in 1932 and is a national program that annually evaluates and identifies new garden seed varieties with superior garden performance based on impartial trialing at 47 sites throughout North America. The horticultural garden at the West Central Research and Outreach Center in Morris, Minnesota is home to one of these test sites. More information on this evaluation program can be found here.

  • Look for information on cultivar introductions and evaluations from universities and their affiliated Extension services in the Upper Midwest.
  • The University of Minnesota's Department of Horticulture is home to research programs that develop cultivars of turf grasses, herbaceous perennials, ornamental shrubs and trees, and fruit crops. Cultivars developed through the efforts of these research programs are highlighted here in a publication titled Minnesota Hardy. Information on garden plant selection can also be found on the University of Minnesota Extension Garden web page.

  • North Dakota State University's Department of Plant Sciences has selected 42 ornamental shrub and tree cultivars that perform well in North Dakota's Zone 3, low moisture climate. Many of these cultivars perform well in Minnesota too. Information on these cultivars can be found here.
  • Ask for information from your knowledgeable gardening friends, garden center staff, and any landscape design and maintenance professionals whose objective knowledge you value. Cultivar information provided by knowledgeable friends and objective horticultural professionals may be anecdotal, but this is often the best information we have given the dwindling support for formal plant evaluation programs. These are the people who will know plants that have stood the test of time in Minnesota landscapes.

    Visit the Minnesota Landscape Arboretum grounds and website regularly to view plants that are hardy enough to grow in Zone 4 and sometimes Zone 3. The arboretum is home to thousands of ornamental cultivars of annuals, herbaceous perennials, ornamental shrubs and trees, and vegetable and fruit cultivars.

  • Information on the locations of cultivars of particular interest to you is readily available from arboretum staff.

  • Use the arboretum as an outdoor classroom. A few visits during the year can provide you with practical information on cultivars of interest to you. Observing plants during their seasons of interest whether it is during bloom display, fruit display, fall color, or in winter, can be most helpful. Visits in late summer and early fall to view overall plant appearance give good visual information on how well a plant has tolerated disease and insect pests throughout the growing season.

  • Check out the plant labels as you observe perennial herbaceous or woody cultivars you are interested in. Labels of plants in permanent plantings will have an 8-digit number on them. The first four numbers will give you a close approximation of the year the cultivar was planted, plant age, and how long the plant has been growing at the arboretum. For example a label reading "19880247" indicates a plant that was planted in 1988 or shortly afterwards.

  • Kathy Zuzek

    Photo 2: Plant Info link on the arboretum website

  • Check out the Plant Info tab on the arboretum website.

    A visit to this webpage can provide information on wholesale and retail nurseries that provide mail order service and carry your plant of interest. The webpage also has links to and lists of other websites, books, and magazines carrying information about and photos of your plant of interest.

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