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April 2010 Archives

What Should I Do With My Ash This Year?

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

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Photo 1: Declining due to EAB. Jeffrey Hahn.

With the discovery of emerald ash borer (EAB) in Minnesota last year, people with ash on their property are concerned about possible attacks from EAB and what they should do, if anything, to protect their trees. Insecticides are an effective method to protect your ash from EAB but does this mean this is what you should do? There are a number of factors that people should consider when weighing their options.

The first factor you should consider is how far are you from a known EAB infestation. The general guideline is that the highest risk from EAB occurs when you are within 10 -15 miles from a known infestation. Right now, EAB is only confirmed in St. Paul and Minneapolis. This means that essentially all of the Twin Cites metropolitan area is at a high risk. However, if you are in Minnesota outside of this 10 - 15 mile radius, the risk from this exotic borer, while not zero, is much smaller and treating your ash for EAB is not suggested.

You should also ask yourself what condition is your ash in. When trees are healthy or at least mostly healthy, i.e. dieback or decline in the canopy does not exceed 40% - 50%, they are a possible candidate for treatment. If the trees are in poor health and the canopy shows over 50% dieback or decline, it's not worth saving the tree. Also, when a tree has suffered significant girdling damage from borers, its ability to move insecticide through the tree to protect it is greatly reduced.

How valuable is your ash to you? Does it provide shade for your house; is it an important part of the aesthetics of your yard; does it has sentimental value? Or is it just another tree in your yard and it wouldn't be missed? The more valuable your ash is, the more likely you will try to save it.

You should balance these factors with the cost of treating trees versus the cost of removing and/or replacing trees. When considering insecticides, remember that the cost will vary according to how large the tree is, how many trees you are treating, what insecticide is being used, and the fees charged by individual companies.

It is very important to remember that once you start using insecticides, it is a long term commitment and you need to continue to treat your ash regularly (every 1 - 2 years) for the life of the tree. Ash do not develop any resistance when they are treated, so if you stop using insecticides after a number of years, they are just as vulnerable to EAB as they were before you started to treat them. So while the cost of a removing a large ash may be considered to be expensive by some, it is a one time cost compared to the ongoing, long term price of treating trees.

What is the right action for you to take? There isn't one right answer. What a person may do will depend on their particular circumstances - the right solution for one property owner may not be appropriate for someone else. However, consider the above factors to help you make a decision that is right for you.

Planting Bare-Root Woody Plants

Kathy Zuzek, University of Minnesota Extension Educator

Spring is here bringing planting season. Early spring between the time that the ground thaws but before bud break is one of two optimal times during the year for planting bare-root trees and shrubs.

What is a bare-root plant?


Photo 1: A bare-root tree dug from a nursery. Gary Johnson.

The name says it all. Bare-root nursery stock are trees and shrubs that are field grown for one to three years, undercut and dug in fall and spring, handled with no soil left around roots (Photo 1), and stored with moist roots and dormant tops at a temperature a few degrees above freezing until they are planted. If you have never seen undercutting in action check out this You Tube video:

Advantages and Disadvantages of Bare-Root Plants

Bare-root stock offer several advantages:

  • Bare-root plants are usually ½ to 2/3 of the cost of containerized or balled & burlapped plants because bare-root plants are easier to handle, store, and ship.
  • Longer root lengths are possible on bare-root plants since weight of the soilless root ball is minimal.
  • The entire root system of a bare-root plant can be inspected so deformed, circling, and broken roots can be detected and corrected or removed.
  • Appropriate planting depth is easy to gauge because the root system is visible.
  • Because there is no soil around the root zone, there is none of the dramatic change in soil interface between the rootball and native soil that can hinder plant establishment.

There are also disadvantages to planting bare-root trees and shrubs:

  • The range of plant sizes and plant types in bare-root plants is smaller. Bare-root trees are usually a 2" caliper or less, because larger sizes do not transplant well as bare-root plants. Caliper is the diameter of a tree stem, measured 6" above the ground. If that stem diameter at 6" above the ground is greater than 4", move up the stem another 6" and measure the diameter at 12" above the ground for your caliper measurement. Evergreens are not sold as bare-root plants unless they are very small seedlings.
  • Bare-root plants should be dormant when planted so there are seasonal restraints to planting.
  • Early spring between the time that the ground thaws but before bud break is one time to plant bare-root plants. Autumn is a second good time to plant bare-root stock. Soil temperatures and moisture levels encourage active root growth at these times of year and lower air temperatures and dormant crowns help to minimize transplant shock.
  • Careful handling of bare-root stock is important. The exposed root system cannot be allowed to dry out during handling, transporting, or planting.

How to Plant Bare-Root Woody Plants


Diagram: Planting a bare-root tree. SULIS.

Never allow the roots of your bare-root plant to dry out between purchase and planting.

Keep the roots moist and protected from wind and sun. If you can't plant immediately, place the plant in a cool, shaded, sheltered location and cover the roots with moist straw, hay, damp burlap, or loose moist soil.

Bare-root plants lose up to 95% of their roots when they are undercut and removed from a nursery. After transplanting it is hard for this reduced root system to absorb enough water to meet the needs of the plant. Until the root system grows and reestablishes to its normal size, a newly planted tree or shrub often experiences transplant shock, which is primarily drought stress. You should plant and care for your bare-root plant in a way that provides the optimal environment for root growth and replacement during the first few years after transplanting.

Optimal planting and care include:

  • A planting hole only as deep as your root system's height. This prevents settling and all of the stresses caused by deep planting.
  • A planting hole at least 2-3 times as wide as the root ball that allows for rapid root growth through the backfill soil before hitting growth-slowing compacted soil outside of the hole.
  • A planting hole with sides that slope towards the base of the hole. The majority of a woody plant's roots grow in the top foot of soil and a planting hole with sloping sides encourages new roots to grow horizontally and towards surface soils.
  • A planting hole backfilled with the original soil. Adding amendments to improve soil quality doesn't help and sometimes hurts by causing poor water drainage in the planting hole. Your time is better spent digging a wider planting hole than amending soil.
  • Adequate watering until the plant replaces missing roots. Water is usually the most limiting factor affecting plant growth after transplanting. Because your bare-root plant has lost the majority of its root system, it relies heavily on water in the root ball through the first growing season. For a bare-root tree with a caliper of 2" or less that is planted on a well-drained site, apply 1 to 1 1/2 gallons of water per inch of stem caliper daily during the first week after planting, then every other day for 1-2 months , and weekly after that until the plant is established.

Establishment Tips for Bare-Root Woody Plants

How long does it take for a bare-root tree to become reestablished? That depends on genetics, environmental factors, and tree size. A good rule of thumb for Minnesota though is to assume that it will take 1 ½ years of time for each inch of stem caliper. So a 1" caliper tree will replaces its roots in 1 ½ years while a 2" caliper tree will take 3 years.

  • A 3" layer of organic mulch instead of turf under the canopy of your tree or shrub. Organic mulch eliminates the competition for water and nutrients that sets up between roots of grass and woody plants, suppresses weeds, retains soil moisture, buffers soil temperatures, protects stems from mechanical injury, and adds organic matter to the soil. Make sure that your mulch is pulled back a few inches from stems to eliminate direct contact.
  • No pruning except to eliminate problems and to ensure good branch structure. Remove diseased, dead, broken, crowded, and crossing or rubbing branches or to encourage a central leader, to eliminate narrow branch crotches with included bark, or to remove basal sprouts on trees. Leaving as much of the crown intact as possible maximizes photosynthate production that can be used to promote root and trunk diameter growth.
  • No quick-release nitrogen fertilizers in the planting hole. Direct contact between quick-release fertilizer and roots will burn the roots. Slow-release and organic fertilizers can be incorporated into the backfill soil. See the trees, shrubs, and fruits section of for more information.
  • Staking if your new tree is densely-crowned and planted on sites with lots of wind exposure. Attach stakes with flexible web belting or any other strips of wide, soft, but strong materials low on the tree trunk. This will prevent movement of the lower trunk and the root system, but allow for movement and resulting strengthening in the top of the tree. Staking may be necessary for 1-3 years while roots are growing and beginning to stabilize the tree. Check the attachment points of the webbing or strips on the stem every 3 to 6 months and loosen if necessary. For more information see: We are sorry, this link is no longer available.
  • Trunk protection for smooth-barked species such as crabapples, lindens, and maple will prevent injury from sunscald. Apply paper tree wraps or white wraps made from synthetic material from the bottom up in an overlapping pattern until the first major branch is reached. The wrap can be secured with duct tape or expandable plastic tape. Apply tree wraps in late October or early November and remove in March or early April.

Lawn Grass Varieties, Seed Labels, and What to Plant Where

Bob Mugaas, University of Minnesota Extension Educator

This is the third and final article in a series of articles related to choosing and selecting the best MN adapted lawn grasses for this area. This last topic will address the topics of what to do when you can't locate the particular grass varieties you've identified, how to read a grass seed label to know what you're really buying and some suggestions for the kind of grass seed mixes to use in various locations around our home landscapes. The previous posts are listed here: 

Series: Choosing and selecting the best MN adapted lawn grasses

Tips for selecting the best available grass seed varieties


Photo 1: Kentucky bluegrass seed sold in bulk. Karen Jeannette.

Selecting and then finding specific varieties of grass seed is not always as easy as you might think. Unlike the relative ease of finding your favorite tomato or marigold varieties through seed catalogs or the internet, looking for specific grass varieties can be much more challenging. It can be quite frustrating to go to a local garden center expecting to find at least some of your particular grass varieties but not see one of them listed on any of the grass seed labels carried by that retail outlet. Instead there are varieties listed that are completely unfamiliar to you. So, what's a person to do?

First, it's important to remember that not all varieties from a seed grower/supplier available in the marketplace will have gone through one of the state and/or national evaluation programs mentioned in last month's article. Indeed, seed growers and some supply companies will have also conducted their own independent variety research. From that research, they will make determinations about what varieties would be suitable for use in mixes to be packaged and sold in the retail or wholesale market.

Second, availability of particular varieties can also be a function of supply and demand characteristics. In some cases, the demand for a particular variety or varieties for use in larger wholesale markets (as well as for sod production) can exceed the supply of those varieties leaving little or none left to be packaged into the homeowner available quantities. In other instances, the availability of seed from particular varieties may be quite low for that year due to a number of possible causes (e.g., poor seed production, adverse weather conditions, etc.) Once again, those particular varieties may not show up either in commercial wholesale mixes or in the seed mixes available at local garden centers or retail outlets.

Finding recommended grass varieties, or the next best thing

So, that still leaves us with the question of "What's a person to do when they can't find the particular varieties they've identified?" One thing that can be done is to jot down the names of the varieties that are listed and go back to the resources mentioned in last month's blog and see if you can find anything about those particular varieties. As with many other things that we purchase, cheaper prices can mean lesser quality. The same would also be true for purchasing grass seed. In general, high quality, 'clean' seed will generally cost more but will almost always provide better results. Staying with reputable, highly regarded name brands of grass seed is usually a good first step even though the specific varieties you were looking for don't seem to be contained in the packages. In other words, the suppliers will most likely still try to provide good quality cutivars that will in turn help the end user, you and me, to achieve good results with their seed mixes. It's also important to remember that seed cost is usually going to be the least expensive item relative to the work and preparation needed to ensure the conditions necessary for successful seeding. Buying cheap, poor quality seed, can jeopardize a project's success no matter how careful all of the preparation work might have been done.

Interpreting the grass seed label

The next logical question one might be asking is "How can I tell if I'm getting both good value and quality in a seed mixture?" That question can best be addressed by examining the different parts of a grass seed label for information that can shed some light on grass seed quality.

Determining what is high quality seed need not be that difficult. Purchasing high quality seed can be easier if you understand a few basic terms on the grass seed label. Figure 1 is a fictitious grass seed label that will be used to discuss the various components of a label. All labels must provide information about the grass seed purity, its germination potential, crop seeds present, weed seeds present, noxious weeds present, and inert components in the package.

Much of the grass seed available in Minnesota comes from the west coast states where climates are most favorable for seed production. However, the very northern reaches of Minnesota are also home to a number of large, well established grass seed production farms. Seed from that area is also available through various outlets in Minnesota. Below Figure 1 is a list of terms you will find on grass seed labels and what they mean.

Terms Found on Grass Seed Labels

  • Lot number. This identifies the larger seed lot from which this particular seed came from. If there are issues related to the purity or growth of this mix, the lot number can be very important in tracing back to where problems might have originated.

  • Test date (month/year) It is always important to buy 'fresh' seed, that is, seed that has been tested within the year when it is purchased. This information tells when the seed was tested and determined to have the characteristics described further on in the label. It is also a useful date when one is trying to determine how long a particular bag or box of grass seed might have been stored and whether it will still grow or not. In general, it is usually better to buy new, fresh seed if more than two or three years old. This will be especially true if the seed has been stored anywhere else other than in cool to cold, dry storage. In most cases storage in garages or basements will not provide the necessary storage conditions to retain good seed viability. Again, in the bigger scheme of things and relative to the seeding preparation investment, the purchase of fresh, good quality seed is likely to be the least expensive part of the project. Bottom line: Always purchase and use fresh seed!

  • Variety These will be the names (when possible) of the actual turfgrass varieties contained in the mixture. In some instances, you will notice a generic term for a species of grass but no specific variety listed. For example, you might see the term 'creeping red fescue, VNS'. The VNS indicates 'variety not stated'. In other words, you know that you are getting a percentage of creeping red fescue but not which specific variety it may be. One shouldn't necessarily consider the term VNS to mean that the grass contained in the mix is a bad grass variety. There could be a number of valid reasons for not being able to list a particular variety. In most cases though, good quality seed mixes will usually try to list specific varieties whenever possible. 

  • Purity (Pure seed) is the percent by weight of pure seed, crop, weed, and inert ingredients in the package. These percentages added together should total 100 percent. Purity is concerned only with quantity, not quality. That is, not all seeds present in the package are capable of growing. To determine the seed that will actually grow or what is known as pure live seed, the percentage purity should be multiplied by the germination percentage. In this example, 31 percent by weight is Kentucky bluegrass (purity). The germination percentage for that variety of Kentucky bluegrass is 80. If one multiplies the purity value times the germination value you will determine how much of the seed will likely grow (under favorable conditions). When carrying out this calculation you will come up with a value of 24.8%. In other words, of the 31% Kentucky bluegrass contained in the mix, 24.8% of it actually has the capacity to germinate and grow. It should be apparent that you should always seek to purchase the highest purity of grass seed compared to the other contents and the highest germination percentages as possible.

  • Germination is the percent of pure seed that will germinate and grow in an ideal laboratory environment during a prescribed length of time. Since field conditions rarely duplicate these laboratory conditions, it is especially important to purchase seed with the highest germination percentage possible. As noted above, this is the percentage used to determine pure live seed.

  • Crop is the percent by weight of seeds normally considered to be grown as an agricultural crop such as grain. This can include other types of grasses that may be undesirable in a lawn. This percentage should be as close to zero as possible.

  • Weeds refer to the percent by weight of all seeds in the package that are not otherwise listed in pure seed or crop. It is not required to identify these weeds or how many there are since this is on a percent by weight basis. For example, one or two large seeds of a weed would pose no particular threat to the new lawn. However, even a small percent by weight of very small seed could account for thousands of weed seeds distributed over the area. This percentage should always be as low as possible.

  • Noxious weeds are listed as the number per pound, not the percentage per pound. Noxious weeds are weedy plants considered by individual states to be very difficult to control and that could pose hazards to both humans and livestock. While this is often more of a problem in farm crop seed, one should always purchase grass seed without the contamination of any noxious weeds.

  • Inert is the percent of material contained in the package that will not grow under any condition. Broken and damaged seeds, chaff, and empty seed hulls are just some of the more common inert material included. Obviously, this percentage should be as low as possible.

First Things First: Right Grass Seed - Right Place - Right Function


Photo 2: Side-by-side comparison of Kentucky bluegrass and fine fescue grass species. Bob Mugaas.

The final information in this article is intended to provide some help in choosing a particular mix of grass seed for particular areas and uses in our yards.
  • Avoid the temptation of a one-seed-mix-fits-all approach to purchasing grass seed for your property.
  • Pay special attention to site differences that may require a different mixture of seed to perform well. The most obvious of these conditions is for one area to be shady while the other part of the yard is in full sun.
  • It may be necessary to choose multiple grass seed mixes for the same residential site in order to have the best adapted grasses planted in the different site conditions. Below is a guide to a number of possible grass seed mixes to fit various needs.
  • Choosing the right plant for the desired location is of utmost importance for long-term plant health. 
  • Match the intended use of the lawn area with the proper types of grasses when choosing turfgrass varieties, blends or mixes. See below for site examples to help you match appropriate turfgrasses with the intended site and function.

Site Examples: Matching lawn site and function to seed varieties

Full-to-partly sunny conditions with minimal traffic or wear, low-to-moderate inputs intended.
  • 60% to 70% Kentucky bluegrasses, 20% to 30% fine fescues, ~10% perennial ryegrass.
Site 2:
Full-to-partly sunny conditions with moderate-to-high levels of traffic and/or wear, moderate-to-high inputs required for rapid recovery:
  • 75% to 85% Kentucky bluegrass, ~15% to 20% perennial ryegrass.lawn for partshade.jpg

Photo 3: Area well suited to Kentucky bluegrass fine fescue combinations such as those for site examples #1 or #3.Karen Jeannette.

Site 3: Shaded for a portion of the day or receives partial shade all day with minimal traffic or wear, primarily a dry shade:
  • 65% to 75% fine fescue; 25% to 35% Kentucky bluegrass (shade tolerant cultivars); ~10% perennial ryegrass.
Site 4: Shaded for a portion of the day or receives partial shade all day with minimal traffic or wear; a somewhat moist shade:
  • <30% to 40% fine fescue; 25% to 35% Poa trivialis, 20% - 30% Kentucky bluegrass (shade tolerant cultivars) ~10% - 15% perennial ryegrass.
Site 5: Full sun-to-very light shade, little to no inputs intended

  • 70% to 85% fine fescues; 10 - 20 % common Kentucky bluegrass; 5 to 10% perennial ryegrass.
Notes about using Ryegrass (Lolium perenne) and Roughstalk bluegrass (Poa trivialis) species in grass seed mixes:
  • Be a little cautious when adding perennial ryegrass to a mix. Research has shown that a 50/50 mix of Kentucky bluegrass to perennial ryegrass results in a stand that may be dominated by perennial ryegrass even though there are many more seeds of bluegrass than perennial ryegrass in the mix.
  • Because of the seedling vigor of annual ryegrass, it is sometimes used in general-purpose seed mixes; but almost never in mixes for "elite" or "premium" turf.
  • Note that the bluegrass species, Poa trivialis, sometimes referred to as roughstalk bluegrass, is better adapted to shadier more moist conditions and usually becomes the dominant species over time in that environment. However, because of the potential aggressiveness of Poa trivialis under favorable growing conditions, some people prefer to avoid using it even though it is well adapted to those conditions.

Hopefully, this article along with the other two previously published articles, Know Your Minnesota Lawn Grasses ( and So what are the best grass varieties? (, you'll get a good start on selecting and purchasing the best adapted, highest quality grass seed for your particular situations.

Hackberry Witches' Broom

Michelle Grabowski, University of Minnesota Extension Educator and Jeff Hahn, University of Minnesota Asst. Extension Entomologist

hackberry witches broom 11.jpg

Photo 1: Hackberry tree with witches brooms. W. Cranshaw,

As you look up at the trees this spring, watching for emerging buds or perhaps a returning song bird, you might notice many small clumps of short twigs scattered through the branches of some hackberry trees (Celtis occidentalis). These clumps of twigs are called witches' brooms. Although witches' brooms are present within the trees canopy throughout the year, they are most easily observed in the winter or early spring, before leaves emerge. Hackberry trees growing in open areas, like a yard or along a street, are more likely to have witches' brooms than hackberry trees in a forest. Often one hackberry tree will have many witches' brooms while its near neighbors have none.

Witches' brooms occur when the bud of the tree is injured or infected. Normally, a healthy bud opens to produce one shoot. However, when a bud is damaged or killed, multiple weak shoots may develop from the same point on the branch. Witches' brooms in trees can be caused by a variety of problems. Trees growing alongside roads where salt is applied in the winter may have buds damaged or killed by splashing salt. In some cases, infection of the tree by a fungus, a phytoplasma or even a parasitic plant like mistletoe can cause witches' brooms to form within the tree's canopy.

hackberry witches broom 1 .jpg

Photo 2: Witches broom on hackberry tree, up close. W. Cranshaw,

The exact cause of hackberry witches' broom remains unknown, although two organisms are consistently found within these twig clusters. The first is an eriophyid mite, Eriophes celtis. Eriophyid mites are tiny, measuring no more than 0.5 mm (1/50th inch) long. Even with magnification, people are unlikely to see these mites. Little is known about their life cycle. We do know that eggs are laid in May and mites cluster on the buds, developing until the end of the summer. The second organism is the powdery mildew fungus Podosphaera phytoptophila. The fungus may be seen as a white cobweb like coating growing on the young shoots and leaves within the witches' broom in spring or early summer. Throughout the year tiny brown to black round fungal resting structures can be found on infected buds, but these are best observed with the help of a magnifying glass. How these two pests interact with the hackberry tree is uncertain. One theory suggests that the eriophyid mite causes the witches' broom to form and the powdery mildew fungus takes advantage of the weakened plant and starts an infection secondarily. It is clear that hackberry witches' broom causes little damage to the health of the tree. Trees with numerous witches' brooms have been found to grow vigorously for years.

hackberry witches broom .jpg

Photo 3: Several hackberry witches brooms, up close. Jeff Hahn. 

Since the true cause of the witches' broom remains uncertain, there is no known method to prevent or to control the problem. Gardeners who are concerned about the affect of the witches' brooms on the ornamental value of the tree can prune off severely infected branches. In most cases however, hackberry witches' broom is only an aesthetic problem in the winter months. The flush of new leaves soon to be produced will hide the witches' brooms, leaving only a beautiful green canopy to be seen by the casual observer.

Repairing Spring Flooded Lawns

Bob Mugaas, University of Minnesota Extension Educator

Early spring, before lawns are actively growing (i.e., foliage is still mostly brown) lawn grasses can withstand several days of being submerged without suffering serious damage. If floodwaters are cold (<60 degrees F.), as they usually are in early spring, lawn grasses can withstand being submerged for even longer periods of time.

Moving water is usually less harmful to lawn grasses than is ponded, stagnant water. Ponding occurs in areas of poor drainage or results from water being left behind in valleys and depressions when floodwaters recede. Spring flooded lawn areas where the water has risen and then receded rapidly often escape serious permanent injury and death.

Post flooding lawn care

Once the soil has dried sufficiently such that it is no longer soggy and slushy underfoot, pick-up and remove debris such as wood, glass, stones, sheet metal, paper products along with other forms of junk deposited by flood waters. It is even good to remove thick layers of leaves or other debris that can smother the grass. Debris can be a safety hazard so exercise caution when picking up and handling this material. Debris left behind can later become a hazard to people operating lawn equipment as well as damaging the equipment itself. It should be noted that the drying process may take two or three weeks, perhaps longer, depending on site conditions.

Assessment of potential lawn damage and recovery may not be possible until those areas have dried. Checking for new shoots emerging from the soil or the emergence of new shoots from surviving plants is a good way to make an early assessment of damage. Usually, once regrowth has begun, it will continue although it may take several weeks before the lawn has completely filled in and begun to thicken up.

Often a more significant effect of flooding is the deposit of sediment, primarily silt, over lawn surfaces. This can lead to serious soil layering problems and even death of existing grass.

Lawn repair solutions for floodwater soil deposits less than 1 inch

Core aerification can be one of the most important and beneficial operations conducted where silt deposits are less than an inch and water has not ponded long enough to cause substantial death of the lawn. When the lawn has begun to actively grow as evidenced by new green grass blades appearing, go over the lawn about 3 times with a core type aerifier. This will help improve overall soil structure, improve soil oxygen levels, help break up soil layering problems caused by the overlay of silt and encourage recovery during the remainder of the growing season. A second round of aerification in early September will be helpful in further promoting active turfgrass growth and recovery through the fall period.

Overseeding can also be done at the time of aerification. Be sure that good seed to soil contact is achieved. To prepare a smooth seed bed, break up the aerification cores with a lawn rake or power rake (i.e. vertical mower). If desired, lawn seeding can be delayed until mid-August through early-September. Sodding can be done successfully throughout the growing season.

Lawn repair solutions for floodwater soil deposits more than 1 inch

Soil deposits in excess of an inch and just barely covering the turfgrass plants should be carefully scraped or washed from the lawn surface prior to any reestablishment. This will also help remove any floodwater pollutants left behind that may have a more lasting detrimental effect on the lawn since their concentrations are completely unknown.

If the lawn area is completely buried with inches of silt, then the best renovation strategy may be to accept that the majority of the lawn has already been severely damaged or killed and it will be necessary to reestablish a "new" lawn. Even though the process of silt removal is a lot of work and can be very damaging to existing turfgrass plants, reestablishing a lawn should begin by removing the excess silt as completely as possible. This should be followed by good soil preparation practices whether the lawn is to be seeded or sodded. See Extension factsheet 5775 Seeding and Sodding Home Lawns ( for more information on seeding or sodding a new lawn.

Where soil removal is not possible, rototill or plow the area thoroughly mixing the soil deposits from the floodwater with the existing soil and dead turfgrass cover. This will help restore more uniform soil conditions creating a better environment for grass to reestablish. One of the main goals of this operation is to help break up soil layering problems that can be caused by the silt deposits as well as the old sod layer. Seeding or sodding can be done as described in the above mentioned publication.

Introduction of new lawn weeds

Another problem that may be encountered with silt deposits is the introduction of potentially new and different weeds to the lawn. Therefore, it may be necessary to use pre- and/or post-emergence herbicides where appropriate during the reestablishment process. Make sure to follow labeled recommendations when using any herbicide to avoid injury to the young grass plants.

Extension resources for lawn repair

While dealing with the lawn may be the very least of one's water problems this spring, those needing to repair their lawn can do so once the soil has sufficiently dried. Local County Extension offices should have the publication FO-3914 entitled Lawn Renovation for additional information on repairing lawns. (The online link is:

Rove Beetles

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

An interesting sample was received from northwest Minnesota in March during a week when the weather was unseasonably warm. More than 20 insects were found on the carpeting in a couple of rooms in a Senior citizens' home. They were worried that they would be damaging and spread to other areas of the building.

The insects in question are a species of rove beetle. Rove beetles are very common insects, although the are often overlooked by people. Most are small, 1/16th - 1/8th long and are conspicuous because of the short wing covers they possess which leaves much of the abdomen exposed. Rove beetles are often associated with dead animals and dung as well as on the ground under stones and other debris. They are predaceous on other insects.rove beetle howard person.jpg

Photo 1: Rove beetles. Howard Person.

Fortunately, rove beetles are not harmful to people or our property. They do not reproduce indoors and are just a temporary nuisance. It is likely that these particular beetles overwintered near the building and wandered indoors when warm temperatures arrived. The use of a vacuum or some other type of physical removal is the only necessary control.

Arboretum Challenge: Veggies by the Yard

Leslie Cooney, Membership Services Manager, Minnesota Landscape Arboretum

Are you thinking about your gardens? Starting seeds? Planning a vegetable bed? Need a garden plan?

The Arboretum is issuing a challenge to all gardeners out there to plant and compare with something we're calling "Veggies by the Yard." Part of our summer exhibition on Powerhouse Plants, we're going to find out just how much food can be grown on a 4x12 ft. plot. Our website offers several vegetable garden plans to choose from:

We'll keep a harvest tally of our yields and ask you to do the same - entering the data online every Saturday June through September. It's a chance to go head to head with Ted Pew, our valiant veteran veggie guy and landscape gardener extraordinaire! raised bed_medium.jpg

Photo: Will you be planting one of the Veggies by the Yard garden plans this year? Karen Jeannette.

Find out more about how you can participate in the Minnesota Landscape Arboretum's Veggies by the Yard by visiting:

April 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor; excerpts from the 2010 Minnesota Gardening Calendar.

Plant tips

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Photo 1: Soil sample from a shade garden area. Karen Jeannette.

Prepare Your Soil


Need ideas for the vegetable or edible garden?


  • Fertilize your lawn to keep it growing vigorously enough to help keep weeds out. Wait until you've had to mow it once or twice though, so you know the roots are growing actively and can make good use of the added nutrients. Seep up and reuse any granules that land on hard surfaces such as sidewalk or driveways, then water the fertilizer lightly into the soils so it "catches" and won't easily wash into storm drains when it rains.
  • If you've seen crabgrass appear early in warmer parts of your landscapes (by sidewalks, driveways, or south-facing slopes) in the past, apply a pre-emergence herbicide towards the end of April in the Twin Cities areas, a week or more later farther north. Otherwise, wait until early to mid-May to spread crabgrass preventer. Whether using a traditional product or corn gluten meal, you must water the lawn lightly afterwards to activate the herbicides ability to stop weed seeds as they sprout.

Trees, Shrubs, Flowers


Photo 2: Mulch used for winter protection can be removed gradually as soil and mulch thaw. Karen Jeannette.

  • Begin to remove protective cover from bulb beds, non-hardy roses and perennials in stages as soil and mulch thaw. Don't rush to uncover tender plants, though. Mulch helps prevent them from coming out of dormancy too early, when damaging cold is still a possibility. Rose canes will be okay as long as temperatures hover around twenty degrees, but most flowering perennials will die back when it's that cold.

  • Prune shrubs grown for their foliage rather than flowers, as soon as their buds swell. (Early pruning removes flower buds.) Many shrubs - dogwood, alpine currant, burning bush, and others produce tiny flowers, but they're not showy enough to worry about eliminating them. Wait to prune junipers, yews, and other evergreens until you see this year's new growth expanding. Prune forsythias, azaleas, lilacs, and other flowering shrubs only after they're finished blooming. For more about pruning flowering shrubs to maximize bloom see:
  • Don't prune or take care to avoid wounding oaks from April through October. April begins the period of high risk Oak Wilt susceptibility. If trees are accidentally wounded or pruning is unavoidable, cover the wounds immediately-within minutes-with one of the preferred materials such as water-based paint or shellac. For more information on Oak Wilt, see:
  • Dormant, bare-root trees and shrubs are often sold for planting in Minnesota during the month of April. See this month's article on Planting Bare-Root Woody Plants
  • When is it safe to plant perennials and annuals? Wait until mid-to late May to plant perennials and until after your area is frost free before planting flowering most annuals.  See the MN spring frost-free map to identify when your area is likely to be frost-free:   


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