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October 2010 Archives

Contents: October 15, 2010

In this special mid-month issue of the Yard and Garden News:

  • Bringing Tropical Plants Indoors for the Winter

  • Dodge County Plant Species Investigation ISU (Invasive Species Unit)

  • What's Happening in the Orchard?

  • Calendar and Contributors *new!*

Karl Foord, UMN Extension Educator


Jeff Hahn.

Each fall brings the challenge of not only what tropical plants to keep over the winter, but also how to keep them healthy in the Minnesota winter home environment. Invariably despite all efforts I will provide winter refuge for aphids and mites. It seems like this is the perfect time to use imidacloprid. As a systemic it will control the aphids and has no chance of impacting natural populations of insect predators or pollinators in this environment. However, Imidacloprid will not control spider mites. Why not?

The fact that an effective insecticide will usually not harm a mite seems counter intuitive. After all they are both Arthropods i.e. small creatures with exoskeletons and jointed appendages. Although following this basic pattern, the body structure differences between mites and insects are dramatic. On closer inspection the mite has no antennae, no wings, 4 pairs of legs, an unsegmented abdomen, and simple eyes. Whereas an insect such as a bee will have 3 body parts, 2 compound eyes, 2 antennae, 4 wings, 3 pairs legs, and a 2kf.jpg

Karl Foord.

segmented abdomen. These physical differences reflect a very ancient common ancestor.

The first arthropod fossils date to the Cambrian @ 555 million years ago (mya). From this common ancestor five groups emerged, 1.Trilobites - extinct, 2. Arachnids (spiders & mites), 3. Centipedes and millipedes, 4. Crustaceans, and 5. Insects. The Arachnids and centipedes are more closely related to each other than to the crustaceans and insects. So a lobster is more closely related to a bee than to a spider. Who would have thought? The oldest arachnid fossil dates to the Silurian period 420 mya, while the oldest insect fossil dates to the early Devonian 407 mya. Sometime in the Cambrian period 542 - 488 mya or Ordovician 488 - 433 mya the insect and arachnid lines diverged. During this time the animals diverged physically as well as metabolically. Imidacloprid capitalizes on the metabolic differences.

Insecticides vary in their mode of action, one of which is to interfere with the nervous system. Imidacloprid mimics the action of acetylcholine (a neurotransmitter). The normal functioning system calls for rapid degradation of acetylcholine to maintain control of neural 3kf.jpg

Karl Foord.

transmission; a little like an on off switch. Imidacloprid is not degraded by normal enzymatic control and thus leaves the switch on which overexcites the nervous system and removes control from the insect. Imidacloprid is specific for insect nervous tissue and doesn't affect mites or mammals in the same manner.

I plan to drench the soil in the pots containing tropical hibiscus, dwarf olive, dwarf Cavendish banana, Australian tree fern, two palms, and the climbing fig. I'll not drench the dwarf Meyer lemon or the star jasmine as I expect them to flower next year and know that the imidacloprid is persistent and could harm pollinators. I have read that bees are attracted to tropical hibiscus, but I have never observed bees visiting these flowers.

My only regret in bringing in the house plants is that I know they suffer from low light intensity. Wouldn't it be great if we could all afford a winter greenhouse for tropical like the one at the Minnesota Landscape Arboretum?

Download a copy of the geologic time scale and access Jeff Hahn's article on mite control.

The following case was brought forth by Detective Marian Kleinwort PSI ISU. The facts of the case were:

Paulownia.jpg1. Original purchase 6 years ago as seed from catalog - unknown; plant name - unknown

2. Leaves appear on new stems at the end of May into June

3. Stems grow very fast in summer sometimes reaching 15 ft.; one witness reported that some of the stems grew 12 - 15 inches in one day this summer

4. Witnesses reported that all growth in the picture was from this year's growth

5. No flowers are produced

6. Leaves do not change color in fall

7. Stems are solid early but become hollow later in the year

6. Each year the shoots die back to the ground and new shoots appear

9. Clumps of the plant have been given to neighbors who report that they have had the plant for 3 years

10. A similar plant is believed to have been observed in a neighboring town

Special Investigator Dr. Mary Meyer was called in as a special consultant on the case. Her findings were as follows:

Genus and species Paulownia tomentosa; Family: Bignoniaceae

Common name: princess-tree; Synonym(s): empress-tree

Consulting Plant Psychologist Dr. Karl Foord was asked to explain the bizarre behavior of this plant.

His findings are as follows:

Plant is reportedly hardy to zone 5b. When growing in its adapted environment its leaves will turn yellow in the fall. Apparently the early frosts kill the leaves before they develop color. It appears that the underground trunk tissue is not killed in this climate and new sprouts appear each year. The great vigor of the young shoots is characteristic of this plant. Because the stems never survive more than one year, any flower buds produced in the first year of growth are killed. This is exactly the way my non-northern strain of Redbud (Cercis canadensis) plants behaves. No trunk is ever established and the plant produces several trunk sprouts which die back to the ground each year.

Editor's note: Thanks to Marian Kleinwort, UMN Extension Master Gardener - Dodge County, for submitting pictures of the sample and the facts about the case. Thanks to Dr. Mary Meyer, UMN Horticulture Science Professor, for identifying the plant.

What's Happening in the Orchard?

Special thanks to Karl Foord and Apple Jack's Orchards for putting together the "What's Happening in the Orchard?" video series.

Calendar and Contributors: October 15, 2010

Getting ready to say goodbye to your garden for the winter? U of M Horticulture Science Professor Bud Markhart offers ways to "Spend time in garden now to save money later" in this KARE11 article. (Don't miss the video on the right side!) And remember- when it comes to your garden, it's not goodbye, it's see you later.

*New this month!*
The Yard and Garden News will now feature brief profiles of the contributors! We've asked "What do you like most about your job?" and "What are you passionate about outside of work?" This month will start with the Yard and Garden News Editor, Karl Foord, and the Technical Editor, Bridget Barton.

Karl Foord, UMN Extension Educator; Yard and Garden News Editor
The thing I like most about my job is learning and discovery. For me these are horticultural and biological topics. Such as learning about the importance of pollinators, how insects fly, the variation in the taste of fruits especially apples and strawberries, and how plants respond to their environment. I like capturing information and putting it in a form that is easy for people to absorb, especially visually.

I am passionate about photographing birds and insects in flight. I am passionate about geology the history of the earth and its organisms, and my dogs (Indiana Jones on my right and Moose on my left).


Bridget Barton, UMN Extension Master Gardener State Program Assistant; Yard and Garden News Technical Editor

The best part of my job is the variety! From working with the Master Gardeners to being the technical editor for the Yard and Garden News- every day is something new! I also love the opportunities I have to meet and work with such interesting and talented people. It's been awesome getting to know Master Gardeners from all over the state, and to see the amazing projects they are working on in their communities. I'm lucky to be part of such a unique program!

I am currently working on my Master of Public Policy at the U of M Humphrey Institute. When I'm not at work or at school, I try to spend as much time outdoors as possible. I also love gardening, dogs, trips to Duluth and the Minnesota Twins (even after the disappointing playoffs last week!)

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Contents: October 1, 2010

In this issue of the Yard and Garden News:

  • Brown Marmorated Stink Bug: The Next Invasive Insect Pest in Minnesota?

  • Pollinator Blues, Part I

  • New Oak Leaf Blight Confirmed in Minnesota

  • Damage Assessment and Repair Options for Late September flooded lawns.

  • Lawn Care Tips for October- Yes, Really, Lawn Care in October

  • Garden Calendar

Jeffrey Hahn, Asst. UMN Extension Entomologist


Photo 1: Brown marmorated stink bug adult. David R. Lance, USDA APHIS PPQ,

Gypsy moth, Japanese beetle, multicolored Asian lady beetle, soybean aphid, emerald ash borer. There is a long list of invasive insect pest species that have entered the U.S. and Minnesota and have caused significant problems to crops, landscape plants, or even just as nuisances. An insect that should be on our radar screen that is present in the U.S. but has not been discovered in Minnesota yet is the brown marmorated stink bug (BMSB), Halyomorpha halys. It was introduced from Asia and was first found in the U.S. in Pennsylvania in 2001. It is now known in most mid-Atlantic states as well as in Oregon.

This is a moderate-sized insect, measuring about ½ - 3/4 inch long. Like other stink bugs, it has a shield-like or triangular shaped body. The BMSB is brown with whitish mottling on its body. There are native stink bugs in Minnesota that are also brown and a similar size. The best way to distinguish between them is BMSB has alternating black and white markings on its abdomen. Also look for black antennae with white bands. The immature BMSB look similar but are smaller and lack wings.

Copy of Euschistus prob. tristigmus luridus .jpg

Photo 2: Euschistus sp., a native stink bug species in Minnesota. Jeff Hahn.

BMSB are pests because they feed on fruit, like apples and peaches and vegetables, such as corn, tomatoes, and soybeans. They feed on a wide variety of plants and are also found on many hardwood trees and shrubs and some herbaceous plants, although it is not clear how injurious they are to these plants. This year has seen an explosion in the numbers of this stink bug in many areas were they are already known to occur, causing loss in some crops.

Also watch out for BMSB in the fall as they can be pests by entering homes and other buildings as the weather starts to become cold, much like boxelder bugs and multicolored Asia lady beetles. In addition to their unwanted presence, they also give off a very disagreeable, pungent odor.

It is important to discover this insect as soon as possible when it first arrives in Minnesota so it can be controlled. If you believe you have seen a BMSB, report it to the Minnesota Dept. of Agriculture's 'Arrest the Pest' Hotline at 1-888-545-6684 (toll free). You can also e-mail them at

Pollinator Blues - Part I

Karl Foord, UMN Extension Educator

The Native Wild Pollinator's Perspective


Photo 1: Bumblebee on Cosmos. Karl Foord.

Most everything we do cuts into their territory. We make roads, houses, cities, and factories. We plant grass athletic fields, home owner lawns, double flower sterile plants, and we plant large agricultural fields of corn and beans all of which are in essence deserts for them. We use insecticides targeted for other critters and sometimes damage them in the process. We even mulch our gardens making it difficult for them to find ground based nesting sites. I can hear them singing the Jim Croce song 'Car Wash Blues' and changing some of the lyrics. "I got them steadily depressing low down mind messing 'I can't find no pollen' blues".

Short History of Insect Pollinators

Most animals and birds depend on flowering plants for food or shelter. Most plants depend on pollinators to complete their reproduction cycles. This makes pollinators key players in the ecosystem. It should be emphasized that the flowering plant pollinator relationship is kf2.jpg

Photo 2:Bumblebee on Golden Rod. Karl Foord.

one of long standing. Insects were around long before flowering plants. The oldest insect fossils date back to the Carboniferous (360 - 300 million years ago) and exhibit wings and other advanced features which suggests millions of years of evolution before the Carboniferous. There is still discussion about the timing of the origin of flowering plants. The ancestors of flowering plants diverged from gymnosperms in the early Triassic (245-202 million years ago), and fossils of flowering plants are dated to the early Cretaceous (145 - 65 million years ago). Flowering plants diversified during this time and became the dominant plant form in the late Cretaceous (100 - 65 million years ago). Suffice it to say that flowering plants and insects have been interacting intimately for at least 100 million years and have become quite codependent. So pollination is central to the life cycle of flowering plants and more than 80% of plant species rely on animal pollinators and 99% of those pollinators are insects.

Photo 3: Bumblebee on Golden Rod. Karl Foord.

The Pollinator-phile's Perspective

Pollinators are needed for the successful production of as much as 25% of everything we eat and drink, and we are rapidly depleting their habitats. Granted much of this pollination is done by the non-native honeybee. But as we shall see in next month's article by Marla Spivak these pollinators are facing their own set of problems. We need these native pollinators if for no other reason than help pollinate some of our important crop species as the honeybees face challenges. We are finding that bumble bees are much better pollinators of tomatoes in greenhouse and high tunnel settings than honeybees. This is true for many crops if you remember the pumpkin and its specifically adapted pollinators mentioned in the last issue.

All things considered I would like to join the ranks of the native pollinator friendly assembly,kf4.jpg

Photo 4: Bumblebee on Golden Rod.Karl Foord.

but what is one to do? Before becoming an advocate I would like to explore what I could do on my own without having to persuade some government entity that they should create pollinator plant refuges on the highway right of ways. This requires some consideration. The native pollinators are adapted to native plants but will glean pollen and nectar from cultivated species. All of our cultivated plants were adapted from wild ancestors. This leads me to consider two steps. First, take an inventory of the plants I those closely adjoined to my property, and access how pollinator friendly my homestead might be. Second, consider the array of pollinator friendly species and see what might fit within the existing landscape. I will address each in turn.

As far as the home inventory is concerned, I love dwarf evergreens so nothing there for the pollinators. But I have apples strawberries willows as well as significant patches of sedum and thyme. There is a buffer area on my property that is undeveloped and features phlox in kf5.jpg

Photo 5: Bumblebee. Karl Foord.

the spring and goldenrod in the fall. An adjoining school grassy area is mowed but does not control any weeds so the dandelions do quite well. I have some other plants but I will need to consider when they flower and how many there are to determine their impact.

As to plants attractive to native pollinators, I looked at lists of the plants and found I had my work cut out for me. When do they flower and for how long? What are their growing requirements and will they be bullies or gentlepersons in their interaction with the other plants in the landscape. So my next assignment is to work on this and see if the plant lists can be assembled in a way that the information can be applied to anyone's landscape; this for next time. In the meanwhile please enjoy some pictures of bumble bees showing their long tongues, choice of pretty flowers, and flying capabilities.

New Oak Leaf Blight Confirmed in Minnesota

Michelle Grabowski, UMN Extension Educator

A new fungal leaf blight of bur oak (Quercus macrocarpa) trees has been confirmed in Minnesota. Bur Oak Blight, also known as BOB, was collected by Jill Pokorny of the USDA Forest Service in several central Minnesota counties and confirmed by Dr. Harrington of Iowa State University.

How to Recognize BOB

• Bur oak blight only infects bur oak trees. Leaf spots or blights on other types of oak tree are caused by different pathogens.
• On bur oaks, symptoms first appear in July or August.
• Infected leaves have brown angular or wedge shaped lesions. Leaf veins turn brown and small black spots (fungal spore producing structures) can be seen with a magnifying glass within the brown lesions.
• Infected leaves are often found first on the lower branches. After many years of infection, however, the entire canopy can be infected.
• Healthy bur oak trees typically drop all of their leaves in the fall. Trees infected with BOB, however, often have many leaves that remain attached throughout the winter.


Will BOB Hurt my Oak Tree?
Bur Oak Blight affects leaves late in the season. Because the leaves have had several months to do photosynthesis before disease becomes severe, the tree has had an opportunity to store up energy. One year of infection, therefore, will not hurt the tree.

Unfortunately trees that are infected one year are likely to have the disease in following years as well. Over several years, the disease becomes more severe, slowly affecting more and more of the canopy. This repeat infection puts stress on the tree, weakening it and making it more susceptible to secondary pests like two lined chestnut borer and Armillaria root rot. Both of these secondary pathogens can cause severe damage to the tree.

Where Did BOB Come From?
Reports of damage to bur oaks similar to BOB were reported in Minnesota as early as the 1990's. Before this time, the problem had not been noticed on bur oaks. It is only recently that the fungus that causes BOB was identified as a new species of Tubakia. It is possible that this fungus was present in Minnesota but never noticed, or perhaps was present but the environment was not conducive to disease prior to the 1990's.

On individual trees, spores of Tubakia sp. overwinter on infected twigs, leaves and petioles that remain attached in the canopy. Rain splashes spores from these old infections to the new emerging leaves, resulting in year after year of disease. New trees can be infected by spores splashing onto leaves from a neighboring infected tree. Overall the spread of the disease within a canopy and within a group of trees is surprisingly slow given the large number of spores produced by the fungus.

What Can I Do To Protect my Tree from BOB?
There are currently no fungicides recommended for treatment of BOB, but research is being conducted to determine if a fungicide injection or spray could protect uninfected oak trees and reduce disease in trees already suffering from BOB.

For now the only thing gardeners can do is reduce stress on infected trees as much as possible. Removing turf grass from below a tree and replacing it with wood chip mulch will help to keep the soil moist. In years of low rainfall, trees should be watered to reduce drought stress. Care should be taken not to wound trees with lawn mowers or other yard equipment. Avoid driving cars or other heavy vehicles over the root zone of mature trees. This can compact the soil and cause root damage.

For more information about bur oak blight read 'BOB in Minnesota' by Jill Pokorny, USDA Forest Service.

Bob Mugaas, UMN Extension Educator - Horticulture U of MN Extension and Brian Horgan, PhD. Associate Professor, Extension Turfgrass Specialist U of MN Department of Horticultural Science

Picture 1(2).JPG

Photo 1: Receding flood waters from a public park. Bob Mugaas.

Flooding is not uncommon during spring and summer here in MN. Yet residents of southern MN are experiencing significant flooding this fall. Justifiably, repairing lawns and landscapes is probably not the highest priority. However, should attention turn to wanting to do 'something', here are a few tips regarding the assessment of potential lawn damage and options for repairing them, even yet this fall.

Have flood waters actually done any damage to my lawn? In general, where flood waters have risen quickly to cover the lawn area but also receded quickly (within 2 or 3 days), there has probably been little permanent injury to the lawn. With shorter days and cooler temperatures in fall, lawn grasses are usually able to remain green and alive through brief periods of being submerged. Picture 1. As flood waters recede and the soils dry, soil oxygen levels improve aiding plant growth. In this situation, little to no repair is usually needed.

In many instances, water flowing over river and creek banks gets trapped on your property and is not able to flow back to the river. Picture 2. In this situation, stagnant, flooded turfgrass conditions may persist for several days or longer. Water loss is now a function of evaporation and soil infiltration capacity rather than flowing back into the stream or river. Damage assessment can be done once the water has disappeared from the lawn.

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Photo 2: Ponded areas of water left behind receding flood waters. Bob Mugaas.

Where grass plants appear brown and rotten, it is safe to assume that the grass plants have died and this area will now need to be reseeded or sodded. On the other hand, if the water evaporated or infiltrated the soil within 2-3 days, grass plants may have survived. These temporarily flooded areas may not be as dense as they were prior to being inundated with water and some reseeding can be beneficial to restoring a healthy dense cover of turfgrass (see notes on overseeding later in this article).

In most cases, water continually moving across a lawn surface is less problematic for the grass plants than non-moving, stagnant water. The differences in these two water movement characteristics will often dictate the amount of sediment deposited on that lawn surface. Sediment deposited is often associated with slowing water flow or ponding.

The likelihood of permanent injury to lawn grasses will depend on the depth of that sediment deposit. If deposits are less than 1/2 inch, usually there are no serious problems for home lawn grasses maintained at higher mowing heights and the grass will still be visible above that sediment layer and continue to grow normally. Picture 3. However, even light sediment deposits can form a distinctly different layer of soil that can ultimately create future soil water and nutrient infiltration problems. To help prevent this occurrence, core aerification (two to three passes) over the lawn will break through the sediment layer thus avoiding future soil problems.

Picture 3(2).JPG

Photo 3: Surviving turfgrass following short term submergence. Bob Mugaas.

Core aerification on home lawns can be done this fall once the areas have dried out sufficiently so that the area is no longer soft and muddy when walking across it. Additional core aerification can also be done in the spring just as the lawn is beginning to green up and again around Labor Day next year. This additional aerification in 2011 will help ensure healthier soil conditions that in turn support a healthier lawn.

Where resources may be more limited and aerification isn't possible, brisk raking will help break up that sediment deposit. Again, this can be done once the soil has dried and is no longer soft and muddy underfoot.

Where sediment has been deposited at levels deeper than about 1 inch and the grass is barely visible through the sediment, grass plants will likely die. In these cases, it is usually better to carefully remove some of that material and overseed to restore the lawn area. A thorough core aerification will be beneficial following sediment removal.

The late September to early October time period is a difficult time to successfully overseed and establish a new lawn. The lack of establishment and maturity achieved by the young grass plants often results in very poor winter survival thus necessitating another seeding in the spring. Therefore, we recommend waiting until the ground is cold but not frozen to sow seed (usually early to mid-November). This process results in seed that does not germinate this fall but begins to actively grow in the spring. This is known as dormant seeding and can give lawn seeds a head start on germination and growth next spring. While results of this practice can be variable, when done correctly and Mother Nature cooperates with sufficient snow cover, successful lawn establishment can be accomplished. The good news about considering dormant seeding is that attention can be given to dealing with home and property losses without feeling like something also needs to be done right now to fix a lawn.

A rather unintended consequence of fall flooding is the introduction of new weeds into lawns and landscapes. By late September, there are many annual and perennial weedy plants actively dispersing their seeds. Flood waters can be a significant means of spreading many of those seeds into places where those plants have never been present. While there is nothing to do right now, be watchful for new and different weeds showing up in lawns, gardens and landscape areas next spring and summer. Early removal or treatment with an herbicide is good practice and limits the amount of herbicide needed to achieve control.

While lawns are not a first priority when dealing with other home and property losses due to flooding, at some point down the road most folks will want to restore their lawns, gardens and landscapes thus restoring a sense of 'normal' to their lives. Hopefully, this information will be of help when that time comes.

Lawn Care Tips for October - Yes, Really, Lawn Care in October.

Bob Mugaas, UMN Extension Educator

Picture 1.JPG

Photo 1: Healthy, vigorous late summer lawn.Bob Mugaas.

Even though much of the month of October can be one of the best times for grass growth and recovery, it's tempting to put away our thoughts, practices and equipment used to care for our lawns by the middle to end of September. The reason for this active period of growth is that the lawn grasses adapted to this area (e.g., Kentucky bluegrass, the fine fescues and perennial ryegrass) are best adapted to the cooler and usually moist conditions of spring and fall. See Picture 1. So, with that in mind, here are a few end-of-season lawn care practices that help support actively growing grass plants.

1. Mowing. So long as our grasses continue to grow, we should be continuing to mow as needed. With cooler temperatures and shorter days, mowing intervals usually become longer the later we go into the month. A common question at this time of year is "Should I cut my lawn shorter the last mowing of the year?" One reason to consider somewhat shorter mowing heights in the fall is the decreased (usually) incidence of snow mold come the following spring. Longer matted grass potentially creates more favorable habitat for the snowmold fungus to live and grow over winter. We see the results of that fungal growth the next spring when, as the snow melts and retreats from the lawn surface, the lawn appears covered with grayish or pinkish colored patches indicating the presence of snowmold.

However, reducing the height of a lawn should not be something reserved for only the last mowing. For example, if the lawn has been kept at about 2.5 - 3.0 inches during the growing season and the desire is to reduce that to two inches, then begin the process of gradually lowering that mowing height two to three mowings prior to your very last cutting. That will help the grass adjust to a lower height of cut more gradually instead of being scalped just before going into colder conditions; a more stressful condition for turfgrass. If the grass is still actively growing during October, you may need to mow somewhat more frequently in order to reach and then maintain the lower mowing height. This is because shorter heights of cut require more frequent mowing to establish and maintain them.

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Photo 2: Comparison of mowed (lower left) and unmowed (lower right) leaf covered lawn area. Bob Mugaas.

2. October is the month when leaves drop from our deciduous (leaf losing) trees. The spectacular fall colors of early October give way to leafless trees ready to face the winter months ahead. So, what to do with all of those leaves? A small amount (usually less than a couple of inches) of fall leaves can be left on the lawn surface and ground up with a rotary mower. Be sure to go over them several times such that the remaining leaf particles can more easily sift down into the lawn and soil surfaces. The lawn should look like it was raked when you are done. See Picture 2. If there are still piles of shredded leaves be sure to rake them off of the lawn surface and either compost them or use them as a mulch in other parts of the landscape. Leaves can also be removed from the lawn by picking them up using the mower's bagging attachment (if it has one) and redistributed as a mulch cover in another non-lawn part of the landscape or composted.

3. Early October is an excellent time to apply herbicides to perennial broadleaf weeds such as dandelions, creeping Charlie, clover, and plantain. See Picture 3. Where only a few weeds are present, hand removal can be just as effective as an herbicide. On the other hand, weed control products are now widely available in ready-to-use application containers. Hence, we can spot treat the specific weeds while introducing minimal amounts of herbicide to the environment. Where weeds are more numerous and scattered throughout the lawn, a broadcast application of an herbicide product can also be done. These can be applied either as a granular or liquid product. The products used should be weed control products only and not combined with a lawn fertilizer as this would not be a good time to be applying fertilizer. Always follow product label directions exactly - it's the law. Be sure the weeds (and lawn grasses) are actively growing at the time of application as the product's effectiveness will be much better than if weeds are growing under water stress. If necessary, water the area to be treated a day or two the planned application to help ensure their active growth.

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Photo 3: Common dandelion, a perennial weed effectively controlled with broadleaf herbicides in the fall. Bob Mugaas.

4. It hardly seems necessary or even appropriate to be talking about watering a lawn given the amount of rainfall and flooding issues experienced over the last few weeks. Nonetheless, should October turn dry and remain warm, lawn grasses will likely benefit from an additional watering or two before shutting down for the winter. In general, it's a good practice to not have lawn grasses go into winter conditions severely stressed due to lack of water. We don't need to follow the one inch per week at this time of year due to the cooler temperatures and shorter days. Both of those conditions slow the loss of water from the lawn and hence any watering required can be done at longer intervals. In other words, that same one inch of water per week, (including rainfall), during the summer months might be sufficient for two or even three weeks this time of year depending on weather conditions.

5. Finally, new suggestions for applying nitrogen fertilizers to Minnesota lawns no longer include a late October to early November application. In short, new research here at Minnesota and Wisconsin questions the usefulness of that nitrogen application due to the inefficiency with which it's taken up by the grass plant. Hence, the preferred late season fertilizer application time for Minnesota lawns is around Labor Day to the middle of September. Nitrogen absorption is much better at that time of year and it ensures adequate nitrogen nutrition for the grass plant going into a very active period of growth. For more information on this topic see the article in the August 1, Yard and Garden Newsletter.

Continuing through the fall with few important lawn care practices can help ensure a healthy lawn going into the winter months and a healthier lawn to begin the growing season next spring. Good Luck!

Garden Calendar: October 1, 2010

Starting this month, the Yard and Garden News will move to publishing just once per month for the winter. We'll return to twice monthly in the Spring!

Watch November 1 for an article on the challenges facing honey bees by UMN Bee Researcher, Marla Spivak. Spivak, a nationally and internationally respected entomologist, recently won a MacArthur Foundation Genius Grant for her work on the health of honeybees!

Garden Calendar:

  • The first frost in the Twin Cities Metro area is expected Sunday! Be sure to cover any tender annuals, and keep an eye out for frost damage! Wondering what the historic frost dates are for your area? Look up your city in this handy table from the Minnesota Climatology Working Group!

  • Be sure to protect hybrid teas and other roses that aren't winter hardy here, around mid-month. It's a gamble when canes are damaged when temperatures drop below 20 degrees F. Mounding soil over over the crowns or tying canes is more work, but much more effective than just using Styrofoam rose cones. Just rake leaves over the bases of hardier roses.

  • Tackle garden clean-up chores before cold, wet weather makes them more difficult. Pull frost-damaged annuals and vegetables, cut back damaged perennials, empty large containers and bring them into the basement or garage where they won't freeze and crack.

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