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March 2010 Archives

Emerald Ash Borer is found in Minneapolis

Minnesota Department of Agriculture news release

The Minnesota Department of Agriculture (MDA) confirmed on Thursday February 25 an emerald ash borer infestation in four trees in the Prospect Park East River Road neighborhood of Minneapolis within Tower Hill Park. This infestation is within a mile of the St. Paul neighborhood in which the tree pest was found last year.

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Photo 1: Emerald ash borer galleries. Jeffrey Hahn.

The infestation was discovered through an ongoing survey of ash trees in the vicinity of the South St. Anthony Park neighborhood, where EAB was found in May 2009. While this marks the first time emerald ash borer has been found in Minnesota outside Ramsey County, state officials said the discovery was anticipated. Last fall, scientists determined that the St. Paul infestation had been in place for about three years prior to detection. Since the adult beetles can fly up to 2 miles each year, officials expected that the bug had spread into Minneapolis.

There is quarantine for emerald ash borer in place for Ramsey and Hennepin Counties as well as Houston county in the southeast corner of Minnesota that prohibits moving from those counties any items that may be infested with EAB, including ash trees and ash tree limbs, as well as all hardwood firewood. This quarantine remains in effect in 2010.

The Minneapolis Park and Recreation Board's Forestry Division is responsible for planting and maintenance of public trees on Minneapolis city streets and parkland. The Park Board's forestry division has been working with MDA to prepare for the arrival of EAB. Next steps will include removal of infested trees and an intensified survey of all ash trees in the surrounding area.

For more information on emerald ash borer, go to the University of Minnesota Extension's EAB web page

Pruning Flowering Shrubs to Maximize Bloom

Kathy Zuzek, University of Minnesota Extension Educator

The optimal time of year to prune deciduous shrubs is in late winter and early spring before bud break. Healing of pruning cuts is rapid as spring growth starts and pests that could infect or invade open pruning wounds are dormant in winter. But if maximizing bloom on deciduous shrubs and trees is important, pruning times may change.

Generally, shrubs flowering later in the season (hydrangeas, summer-blooming spiraea, and potentilla), flower on current season's stems, commonly referred to as new wood.  These shrubs can be pruned in late-winter to early spring without reducing bloom.

Spring flowering shrubs (forsythia, bridal wreath spiriaea, and rhododendrons) generally flower on the last year's stems, commonly referred to as old wood. These shrubs are best pruned immediately after flowering to conserve next year's bloom.

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Figure 1: Viburnum 'Emerald Triumph' stem with flower and vegetative buds (click image to enlarge). Kathy Zuzek.

To more fully understand how and when spring blooming shrubs form buds on new and old wood,  enlarge the annotated images in Figures 1 through 5 by clicking on the thumbnail image.  These figures supplement the following pruning examples for Emerald Triumph viburnum and Summer Wine ninebark.

Figure 1 shows a branch of Viburnum 'Emerald Triumph'. The round flower buds at the tips of the 2009 growth will bloom this spring so this plant blooms on "old" wood. The vegetative buds that will produce new stems and leaves during the 2010 growing season are the tall thin buds below the flower buds. Leave this branch unpruned and in spring of 2010, you will have the bloom and new stems and leaves shown in Figure 2. The stems will continue to grow and lengthen through mid-summer. Along these stems, new vegetative buds will form and a flower bud will be produced at the tip. These will be the buds that produce stems and flowers in 2011.

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Figure 2: When the flower bud (a) and vegetative buds (b & c) on the 2009 stem open this spring, flowers and new stems and leaves will be produced (click image to enlarge). Kathy Zuzek.

Now imagine pruning this viburnum sometime in the next 2 months. As you remove or shorten stems, you are also removing any flower buds at the stem tip that would have bloomed in spring of 2010. Pruning in late winter will not affect the plant's health, but it will decrease the number of flowers and fruit produced in 2010.

What if you waited to prune until late this summer? Bloom would be maximized this spring. But by late this summer, new flower buds for the 2011 bloom will have already developed at the tips of this year's stem growth. By waiting to prune until late summer some of next year's flower buds will be removed. Pruning also stimulates new growth and late summer pruning can result in a flush of new growth that will not harden off properly, resulting in winter injury. So pruning in late summer maximizes bloom in spring of 2010, reduces bloom in 2011, and creates the risk of a late season growth flush that would be susceptible to winter injury.

If maximum floral display is important, the best time to prune this shrub is immediately after bloom. The shrub will bloom this spring. After pruning, growth will occur until mid-summer. Next year's flower buds will be found at the tip of this growth by late summer. The plant will harden off properly and will not be injured during next winter. By pruning immediately after bloom ends, a gardener will maximize bloom in both 2010 and 2011.

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Figure 3 &4: Summer Wine ninebark and Summer Wine ninebark pruned to improve plant habit (click image to enlarge). Kathy Zuzek.

Figure 3 shows the normal plant habit of 'Summer Wine' ninebark. Ninebarks are often pruned to control the rampant growth that leads to long stems and the open and loose plant form you can see in the photo. In Figure 4, you can see a specimen of 'Summer Wine' that was pruned into a dense symmetrical plant habit. This plant was pruned the previous spring immediately after it finished blooming, which gave the plant time to set floral buds that led to the next season's heavy bloom you see in the photo.

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Figure 5: Ash tree branch showing a bud scar separating different years of stem growth (click image to enlarge). Kathy Zuzek.

How do you tell where "old" wood ends and "new" wood starts? The vast majority of plants form a vegetative bud at the end of a year's stem growth. As that bud opens and expands the following spring, the bud scales fall off and leave a distinct scar around the stem. Figure 5 shows an example of this terminal bud scale scar on an ash branch. This scar shows where one year's growth ended and the next year's growth started. Oftentimes there is also some difference in stem color between the new stem growth and last year's stems.

Table 1 lists major shrubs, vines, and small trees that grow in Minnesota along with information on whether they bloom on previous year's growth, current year's growth, or both. All of these plants can be pruned in late winter or early spring without affecting plant health. Plants that bloom on "new" wood can be pruned in late winter or early spring without diminishing this year's bloom. Wait to prune plants whose flower buds are produced on "old" wood until immediately after flowering if you want to enjoy the full amount of bloom this spring.

Table 1. Flower bud location on deciduous shrubs, vines, and small trees.pdf

So, what are the best grass varieties for this area?

Bob Mugaas, University of Minnesota Extension Educator

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Resources for turfgrass species selection

Determining and then finding the best lawn grasses for one's lawn is not as simple a task as it might seem. However, there are at least a couple readily available resources about turfgrass species and varieties that are helpful when trying to determine which ones will do well in this area. One of those is a local source from right here at the University of Minnesota. The other is a national database with extensive information about turfgrass varieties. Let's see how we might utilize these to make a list of suitable varieties for this area. UofMN NTEP trials(2) - med.jpg

Photo 1: U of MN NTEP perennial ryegrass trial Bob Mugaas.

We'll begin with a look at the national database known as NTEP, the National Turfgrass Evaluation Program. Their information can be accessed at: http://www.ntep.org. This program is a cooperative effort between the non-profit National Turfgrass Federation, Inc. and the United States Department of Agriculture. It conducts comprehensive evaluations of turfgrass species and varieties across the country in cooperation with researchers at state Universities. (See Photo 1. U of MN NTEP perennial ryegrass trial). The evaluation data is submitted to NTEP for review, analysis and publishing. As a result of that effort, reports are created and made available to anyone wishing to view that data at no cost. For more information about the organization and what resources they can provide, visit their website mentioned above. They also provide a variety of helps to help navigate through the information.

Determining well adapted varieties

Variety information provided by NTEP as well as many others use a very common statistic known as 'least significant difference' or LSD to help aid the user in determining which varieties show true differences from the others being evaluated. This statistic also comes with a probability value that indicates these differences would occur either less than 5% or even less than 1% of the time strictly by chance. Hence, that gives us some level of certainty that the observed differences were not just a chance occurrence but are real differences between the varieties. Fortunately, the LSD and its probability value will have already been determined by NTEP or by the organization doing the data analysis. It is usually found at the bottom of charts that list various variety ratings for a particular characteristic.

For example, when looking down a column of numerical rankings, there can easily be questions about which of these varieties are really superior to all or any other varieties. That would be a perfectly fair question and hence, the need for a tool to help separate the top performing varieties from the rest of the pack. This is where we use the LSD statistic.

Here's how it works. Let's suppose we have the following (fictitious) ranking of bluegrass varieties based on their overall turfgrass quality during the year. In other words, which of these varieties consistently exhibited the best overall turfgrass quality? In this case the rating scale is 1 to 9 with 1 being virtually dead and the lowest quality and 9 being the very best overall turfgrass quality. In most cases, a rating of 6.0 or above would be considered acceptable for a home lawn situation.

TABLE 1

Variety Turfgrass Quality

Variety A 7.1

Variety G 7.0

Variety Y 6.8

Variety B 6.8

Variety M 6.7

Variety J 6.4

Variety S 5.7

Variety C 5.6

Variety R 4.4

Variety H 3.7

LSD 1.3

As noted above, these are all fictitious numbers but they will serve to illustrate how to use the real data presented by NTEP or individually by Universities such as here in Minnesota. Remember the LSD statistic indicates what the minimum difference is between the averages of the different varieties for them to be considered truly better or different than the others. In this case, all of those varieties separated by a difference of less than 1.3 would be considered similar in their turfgrass quality even though they may not have exactly the same average value. Thus, in our example, varieties A, G, Y, B, M, and J would all be considered similar in turfgrass quality. Hence, there should be little to no difference among the first six varieties relative to overall turfgrass quality.

In general, you work from the top down when determining LSD groupings. It should be apparent that you could start anywhere in the column and create a set of varieties that are not significantly different from each other in turfgrass quality. For example, using our LSD of 1.3, we could justifiably say that varieties M, J, S and C are not significantly different from each other. That would be a true statement but, there would be some question as to how meaningful that particular group of varieties would be. In general, we are looking for varieties that rank at or near the top for our particular characteristic, not necessarily those in the middle of the pack. Hence, the reason for beginning at the top and working down the column rather than working from the bottom up or starting randomly in the middle of the column. One can also use the LSD statistic to compare one variety with another rather than creating a particular group of varieties as was just done in the above example.

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Photo 2: Early growth of new U of MN turfgrass evaluation study. Bob Mugaas.

Our own University of Minnesota Turfgrass Program website, www.turf.umn.edu, also has variety evaluation information. Likewise the evaluation data presented in our various research reports is arranged in the same manner as that of NTEP and utilizes the LSD statistic to separate significant differences between particular cultivars or groups of cultivars. Thus, if you would like to know how particular turfgrass varieties performed in this area, check out this website for that information as well as other information about the University of Minnesota Turfgrass program.

Hopefully, this information will encourage you to do some investigating into the turfgrass varieties that have the potential to perform well in this area and in your particular situation. Next month, we'll discuss understanding a grass seed label and what to do when the varieties you're looking for aren't listed on any of the packages of seed you've examined.

Baptisia australis, 2010 Perennial Plant of the Year

Karen Jeannette, Research Fellow and Yard and Garden News Editor

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Photo 1: Baptisia australis 7 years after planting. Karen Jeannette.

The 2010 Perennial Plant of the Year goes to Baptisia australis, also referred to as false indigo. While many times the perennial plant of the year is in fact versatile and well-suited for Minnesota, as with any nationally nominated plant, there are years when the plant of the year does not always turn out as we hope in Minnesota, or is not hardy to any or all of our Minnesota cold hardiness zones ( 2, 3, 4).

 Baptisia australis is considered a long-lived perennial (barring any catastrophe, abuse, or major disruption to the plant or root zone) and is cold hardy in zones 3-8.  


The Perennial Plant of the Year is named annually by the Perennial Plant Association, whose board of directors include plantsmen and women who represent nurseries, universities, botanical gardens, and other horticulture entities. The Perennial Plant Association hosts a Plant of the Year Committee, who votes yearly on one of several previously nominated perennial plants, and then nominates future selections based on the following characteristics:

  • Suitable for a wide range of climatic conditions
  • Low maintenance
  • Pest and disease resistant
  • Readily available in the year of release
  • Multiple season of ornamental interest
  • Easily propagated by asexual or seed propagation

Uses and information about Baptisia australis can be found in the Perennial Plant Association's flyer, as seen here:

baptisia-australis_poy2010-1.pdf


As mentioned in the above flyer, Baptisia australis can be quite useful in prairie gardens, landscapes, or restoration, along with native and related species, Baptisia bracteata (cream to yellow flowers) and Baptisia alba (white flowers).  The University of Minnesota bulletin Plants in Prairie Communities: Characteristics of Prairie Plants lists all three species as being used in mesic plant prairie communities

Purchasing Baptisia australis - don't let its sparse start fool you!

Because Baptisia australis takes three years to become an established, flowering plant, note that when purchasing first year plants sold in one or two gallon pots, they will not be blooming. In fact, the two or three-stemmed potted plant may look a bit sparse next to other quicker to establish perennial plants for sale. However, just be aware that a first year false indigo plant will likely require a little imagination on your part at the time of purchase.  As long as the plant appears in good health (i.e. not wilting, foliage intact, roots whitish with no rot), these first year plants actually hold much potential. Once planted in the appropriate garden site and soil, false indigo will begin the establishment process needed to become the long-lived, drought resistant, cold hardy, and robust perennial performer it has been touted as being.

Pavement Ants During Winter

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

Although it is cold outside, that does not stop some ants from being active in buildings. A common indoor winter ant is pavement ants. A pavement ant is 1/8 inch long and is reddish brown (it can actually range from light brown to dark brown). If you examine a pavement ant closely, you will see a two-segmented petiole, the 'waist' connecting the abdomen with the thorax. With magnification, you can also see a series of fine grooves etched into their heads as well as a pair of small spines on the back of their thorax.DSC_0086a.JPG

Photo 1: Pavement ant. Jeffrey Hahn.

Pavement ants typically nest in the soil, usually under objects, such as stones, bricks, sidewalks, and driveways. When they are found during winter, they are nesting in the soil under the concrete slab. When the nest is kept warm from the building's heat, the ants stay active, move through cracks in the concrete and actively forage for food and water. Ironically, many people that see pavement ants during winter do not see them in the summer when the ants are more likely to forage outdoors. Pavement ants prefer to feed on greasy food, including meats, dry pet food, and peanut butter.

If you are having a problem with pavement ants, first see if you can determine where they are coming from. If you find them moving through a crack, e.g. in an expansion joint, you can try to seal it to help keep pavement ants out of your home's interior.

If this isn't possible, the best long-term control is baiting them. Select a bait that is effective for grease feeding ants and place it where you are commonly finding the ants. Don't be surprised if there is an increase in the number of workers that are active around the bait. They will recruit additional foragers to take advantage of the newly discovered food source.

You might be tempted to spray the ants with a household insecticide but the number of foraging workers represents just a small percentage of the total number of ants in the nest. You can't destroy a nest through attrition by killing the workers you see. You can get some relief from their presence but it will only be temporary and the ants will return. Insecticides will also interfere with the ability of the workers to take bait back to the nest. The less bait that is brought into the nest, the less effective it will be in eliminating it. You can also consider hiring a professional pest control service to treat your ants.

If you ignore pavement ants, they will probably start foraging outdoors as warmer weather arrives, and 'disappear' from inside a building.

Keep in mind that not all ants seen during winter are pavement ants. You may also see carpenter ants, Pharaoh ants, yellow ants, and thief ants. Their habits differ as well as their treatment. If you have any doubt as to what kind of ant problem you have, get them identified them by an expert.

A Cuban Cockroach in Minnesota

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist

Bananas are favorite fruit of many people. Because they are grown only in tropical areas, they need to be imported into Minnesota. Some people have occasionally discovered inadvertent hitchhikers, primarily spiders, that have been accidentally been brought into Minnesota with the bananas. Recently an interesting cockroach was discovered around bananas. DSC_0069.JPG

Photo 1: Cuban cockroach. Jeffrey Hahn.

A person in Morris, Minnesota (in the west central part of the state) found an insect around a sink where some bananas had been sitting. The insect was about 3/4 inch long, pale green, with long antennae and fully developed wings. A quick check of the literature revealed that the insect in question was a Cuban cockroach.

A Cuban cockroach gets it name because it was originally collected in Cuba. It is now commonly found in Mexico, Central America, and northern South America. It is only found in the U.S. in Florida. Although a Cuban cockroach is an outdoor species, it likes to enter buildings and other structures. They particularly are attracted to lights. Cuban cockroaches are also commonly brought indoors on bananas.

Because this cockroach species is native to tropical and subtropical areas, it does not survive long in the upper Midwest. In fact, this particular individual died shortly after it was found. A Cuban cockroach should not be considered a pest when it is found in Minnesota. It is short-lived, does not reproduce in homes, and does not cause any damage. If you find one, just consider it a curiosity.

March 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: March is a good time for pruning out disease. Shown here: Black Knot on Prunus. Karen Jeannette.

  • Inspect your apple or crabapple trees for fire blight so you can prune out all traces of the disease this month. You might also find the blackened, dead branch tips on pear trees or mountain ash. Check also for black knot swellings on chokecherries and other members of the cherry family. Prune at least six inches back in to healthy wood when you remove diseased tissue. If possible, dip your pruners into bleach solution between cuts.

See the following articles from the March 1, 2007 Yard and Garden News to best implement sound pruning practices:Pruning Tools, Pruning Cuts, Pruning Out Galls and Cankers

  • Start seeds that need eight to ten weeks growth indoors under fluorescent lights by mid-month. Sweet alyssum, blue salvia, and dianthus pinks are just a few such seeds. Peppers, eggplants, and leeks are among others. Tomatoes may be started at the same time, but plants will be rather large when you put them outdoors. It's better to wait until the end of the month to plant tomato seeds indoors.

  • Check produce you've kept in cool storage to make sure nothing is turning soft or rotting. Remove anything suspect, as problems can readily spread. Winter squash, onions, apples, and potatoes all have finite storage life, particularly if temperatures are warmer than ideal. Non hardy summer bulbs, roots, and corms such as dahlias, tuberous begonias, canna or calla lillies may also soften or shrivel if temps are too high or conditions too dry.
  • Heavy spring snowfall often weighs down evergreen boughs and flattens newly emerging bulbs. It's probably best to just let the snow melt off on its own. If you prefer to remove it from evergreens, scoop it off gently rather than hitting the branches. They're still brittle this time of year and prone to breakage. Snow won't permanently harm bulbs, though they might not straighten up completely this year.

  •  Fertilize houseplants now that days are growing noticeably longer

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