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Extension > Yard and Garden News > February 2011

Monday, February 28, 2011

Contents: March 1, 2011

In this issue of the Yard and Garden News:

You buy a plant at a garden center. Where did it come from?

Karl Foord, UMN Extension Educator

Vanilla Strawberry™.
Hydrangea paniculata 'Renhy'PP20,670

To answer this question I traveled to Newport, Minnesota to visit with Debbie Lonnee who is a Planning and Administration Manager at Bailey Nurseries. Don't be fooled by the title, Debbie knows hers plants intimately. Listening to her describe plant cultivars is like watching Monet paint.

Bailey Nurseries

Bailey Nurseries celebrated its 100 year anniversary in 2005 and is still managed by fourth generation members of the Bailey family. Bailey has production locations in Minnesota, Illinois, Iowa, Oregon, and Washington where it produces and distributes fruit and shade trees, ornamental shrubs and vines, roses, evergreens, fruits, perennials, and annuals. As a wholesale operation they sell to over 4500 retail garden establishments, landscapers, and growers located in 47 U.S. states as well as Canada, Europe, South Africa, Australia, and Japan. Try to imagine the effort involved in getting this wide variety of plants delivered at the right time of year for each of these locations. It boggles the mind.

Bella Anna™.
Hydrangea arborescens 'PIIHA-1' PPAF.

Endless Summer® Blushing Bride™ Hydrangea.
Hydrangea macrophylla 'Blushing Bride' (PP17,169).

Breeding efforts and partnerships

The breeding efforts focus on improved habit and ornamental qualities, and disease resistance to name a few among a host of characteristics. The disease resistance objective is particularly noteworthy as its goal is to eliminate chemical treatments and to replace plants which have been shown to be particularly susceptible to diseases. Bailey has a breeding program but they do not restrict their efforts to their own program, as they solicit breeding partners from around the world. This greatly increases their reach and at the same time increases our exposure to newly produced plants. To get a sense of how this brings plant opportunities to you and me, I asked Debbie to trace the development of three new cultivars.

New Cultivars

One of the new cultivars is 'Vanilla Strawberry™' which is a Hydrangea paniculata with conical shaped flower. The interesting thing about this cultivar is that the flower starts out stark white and gradually changes from white to pink from the bottom up. This cultivar came from a partnership with SAPHO, an organization formed between French breeders and the Angers branch of the French Research Institute (INRA). Presently there are 20 breeder/stockholders including M. Renault, the breeder of 'VANILLE FRAISE ® 'Renhy'.

Twist-n-Shout® Big Leaf Hydrangea.
Hydrangea macrophylla 'PIIHM-I' PP20,176.

Another new cultivar is 'Bella Anna' which is a Hydrangea arborescens from the Endless Summer® series of reblooming Hydrangeas developed by Dr. Michael Dirr who spent most of his career at the University of Georgia. 'Bella Anna™' produces giant pink flowers that can measure up to 10 inches across. It is in essence a pink 'Annabelle' hydrangea.

It should be noted that H. arborescens does not change flower color in response to soil pH. The three other cultivars in the Endless Summer ® collection (Endless Summer™, Blushing Bride™, and Twist-n-Shout™) are all H. macrophylla species which does respond to soil pH. There are products called Color Me Pink™ and Color Me Blue™ which will change the color of your hydrangea flowers. The flowers become Pink in alkaline soil (pH greater than 7), and blue in acidic soil (pH less than 7).

First Editions® Little Devil™ Ninebark.
Physocarpus opulifolius 'Donna May' PPAF.

A third cultivar is 'Little Devil™' Ninebark which is a Physocarpus opulifolius. This cultivar was bred by Dr. David Zlesak who was the previous editor of the Yard & Garden News and now a professor at the University of Wisconsin-River Falls (UWRF).
One of the advantages of this cultivar is its size. David was able to introduce a dwarfing gene creating a 4 foot tall dark leaved ninebark vs. a 10 foot tall 'Diablo' dark leaved shrub. Much of today's breeding work focuses on creating small stature or dwarf varieties. This permits traditionally larger plants to fit into today's smaller landscapes as well as permitting a greater variety of textures, forms and colors for the landscape palette.

Last spring Twin Cities Live did a short segment on Bailey Nurseries, in which they showed a number of the production systems and facilities. This video is no longer available.

All photos courtesy of Bailey Nurseries.

Where Did Those Annoying Insects Come From?

Jeffrey Hahn, Asst. UMN Extension Entomologist

Photo 1: Boxelder bug.
Jeff Hahn .

It is common during mild winter weather to see various nuisance insects in your home, especially boxelder bugs, multicolored Asian lady beetles, and western conifer seed bugs. Despite the appearance that they have laid eggs and are hatching now, these insects have actually been in homes since fall when they first entered structures.

When they came into buildings in the fall, some insects accidentally moved all the way into homes. Others took refuge in wall voids, attics, and other nooks and crannies. As long as these areas stayed cold, they remained inactive. However, when it became warm, they 'woke up' and moved towards warmth which would be the inside of your home. As we get closer to spring, we see this occurring more frequently. These insects often congregate together in clusters in these harborages so as these areas warm up, not all of the insects become active at the same time. Or they just could occur in places in the home that warm up at different times. The end result is that there will be insects emerging up at different times during the winter.

When you see these insects now, your options are limited. Your best bet is to physically remove them, e.g. with a vacuum. Insecticides are generally not suggested as it will not prevent the insects from emerging and you have to physically remove them whether they are dead or alive. If this is a problem you deal with every year, be sure to target control in the fall before the insects start moving inside. The best tactics are sealing as many obvious spaces that you can find and supplementing that with an insecticide treatment. Once these insects are in your home, there is little you can do.

Understanding and Using Home Lawn Fertilizers

Bob Mugaas, UMN Extension Educator

Photo 1: Applying lawn fertilizer using a rotary spreader.

While it may only be March 1 and there is still plenty of snow covering the ground, in a few short weeks our attention will be turning to taking care of our lawns and gardens for another year. One of the spring activities that many homeowners focus on is getting their lawns off to a healthy, vigorous start; an activity that usually means applying some fertilizer to the lawn. Appealing to that desire is the rather large array of home lawn fertilizers available at local garden and home improvement centers. Frequently, that leaves the homeowner asking the question, "Which one should I buy?" or perhaps even asking the question, "Do I really need to fertilize my lawn at all?"

Over the next three months and beginning with this issue, the emphasis of this lawn care section will be on information to better understand the basics of lawn fertilizer packaging. In turn, that should help with the decision about which one to buy and some tips on getting the most from that fertilizer product.

Plant Nutrient Needs

Photo 2: The basics of photosynthesis.

Before launching into fertilizer product labeling, it's important to review why we would want to fertilize our lawn in the first place. Grass plants growing in our lawn are no different than any other green plant in that through the process of photosynthesis they manufacture all of their own needed food. See Picture 2. Biologically, we call them autotrophs. That is, we don't 'feed' out plants directly they make what they need for growth using elements or nutrients obtained from the soil or atmosphere. The three elements needed by the grass plant in the largest quantity are carbon (C), Hydrogen (H) and Oxygen (O); all of which are obtained from the air or water.

Beyond those three, the elements needed in the largest quantity to support healthy grass growth are nitrogen (N), phosphorus (P) and potassium (K); the majority of which are taken up from the soil by the root system. These three are known as primary macronutrients. In addition to these primary macronutrients, there are considered to be about 10 or 11 other essential nutrients to support healthy growth. These too, are all extracted by from the soil by plant roots. However, it is the primary macronutrients of N, P and K that are often insufficient in soils to sustain and support healthy grass growth. Hence, they often need to be supplemented in the form of fertilizers to provide an ongoing supply of these nutrients throughout the growing season.

Soil Testing to Know What's Needed

The only reliable way to determine what may be needed in the way of nutrition is to take a soil test from the lawn. Soil samples taken or sent to the University of Minnesota Soil Testing Lab for analysis will provide results regarding soil pH, organic matter content, an approximation of soil texture and the amount of available P and K present. They will also provide a basic interpretation of these results along with recommendations for what, if any, fertilizer might be needed for the lawn.

It is beyond the scope of this article to go into the details of taking a soil test or interpreting the results. However, additional information about taking a soil test can be found at the Soil Testing Lab's website . Additional information about interpreting soil test results can be found in the Extension publication Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants

Remember Minnesota's phosphorus law!

Taking a soil test is always a good first step to determine what one might be looking for in the way of a lawn fertilizer. It is especially important in Minnesota as we have a state law that restricts the application of any fertilizer containing phosphorus to lawns without a soil test that indicates a need for additional phosphorus or a new lawn is being established, either by seeding or sodding, when additional phosphorus can be added to aid in the early growth and establishment of that lawn. Thus, without either of those two conditions being met, it is against Minnesota law to apply any fertilizer containing phosphorus to an existing, established lawn.

So, what's in that lawn fertilizer bag anyway?

When looking at a lawn fertilizer bag, the most common container for lawn fertilizers, there will always be three numbers present that state, from left to right, the amount of nitrogen, phosphorus and potassium contained in the bag. This specific ratio of N-P-K is known as the fertilizer analysis. For example, a bag of lawn fertilizer with the analysis of 25-5-15 would be 25% N - 5% P - 15% K. This is also known as the guaranteed minimum analysis as the fertilizer bag cannot contain any less than the percentages stated on the bag for the respective nutrients. Because this is a guaranteed minimum analysis, by law the bag could contain more than that stated but cannot be less. This fertilizer analysis is a percentage by weight basis. That is, if a bag of fertilizer with the above analysis weighed 50 pounds, then it would contain 12.5# N (50 x 0.25), 2.5# P (50 x 0.05) and 7.5#K (50 x 0.15) for a total of 22.5# of nutrients in this 50# bag of fertilizer.

The difference between the amount of nutrients contained in the bag and the total weight of the bag is largely attributed to the weight of the carrier. That is, the material used to bind to the nutrient or 'carry' them such that it can be applied using various types of spreaders. Frequently, these materials are in the form of dry granules that help disperse the fertilizer uniformly across a lawn surface when applied through a spreader.

The fertilizer analysis gives the percentages of N, phosphate (P2O5) and potash (K2O) contained in the bag on weight basis. The percent nitrogen is considered to be the actual amount of nitrogen contained in the bag while phosphorus and potassium are given in their oxide forms (i.e., they are combined with oxygen). For example, the element phosphorus only makes up 44% of the molecular mass of P2O5. Thus, in order to determine the amount of actual phosphorus contained in the bag we must multiply the percent phosphate in the fertilizer bag by 0.44. From our example above, the 5% phosphate equates to 2.2% or 1.1 pounds of actual elemental phosphorus in our 50# bag. Likewise, the element potassium makes up 83% of the molecular mass of the K2O molecule. Thus, in our example above, we would multiply the 15% by 0.83 to determine the amount of actual K present in the bag. Carrying out that multiplication we get 12.45% actual K or 6.22 pounds of actual K in our 50 pound bag.

Unless there is a specific need to know the amount of actual phosphorus or potassium present in the bag we usually use the percent phosphate and potash for making fertilizer recommendations. Most soil test recommendations also base fertilizer needs on these same phosphate and potash percentages. Hence, when applying the amount of phosphate or potash suggested in the soil test recommendations, one will be applying the needed amount of phosphorus and potassium to the lawn. Picture 3.

Coming up

In next month's article, we will be taking a close look at the nutrient nitrogen as it is the nutrient required in the largest amount next to C, H and O. It is also the nutrient for which nearly all rates of lawn fertilizer applications are based. And, it may just be the reason why you would select one fertilizer over another. Check in next month for a thorough overview of this very important fertilizer nutrient.

Black Knot of Plums, Cherries and other Prunus sp.

Michelle Grabowski, UMN Extension Educator

Although very few plant diseases are active in the landscape during the cold winter months of Minnesota, winter is a good time to check trees and shrubs for branch infections like cankers and galls.

Photo 1: Black knot gall.
M.Grabowski, UMN Extension.

One common gall forming disease of Prunus species is black knot. This fungal infection causes swollen lumpy wooden black growths to form along the length of infected branches. In the winter, with no leaves to hide them black knot galls stand out and can be easily found within the canopy of infected Prunus trees.

Black knot is caused by the fungus Apiosporina morbosa, and infects over 25 species of Prunus. This includes fruit bearing trees like sour cherry (P. cerasus), European plum (P. domestica) and American plum (P. americana), as well as wild Prunus species like pin cherry (P. pensylvanica) and choke cherry (P. virginiana). Ornamental trees and shrubs like flowering almond (P. triloba) and purple leafed plums (P.cerasifera) can also be infected. There are a few disease resistant fruit tree varieties, but unfortunately most are not hardy in Minnesota.

Photo 2: Black knot infection on a trunk.
M.Grabowski, UMN Extension.

Black knot galls are elongate, knobby growths that grow parallel to the length of the stem. When young, galls may appear olive to brown. They then turn black when mature, and may crack and crumble with age. Galls are a combination of fungal tissue and wood, so that galls will be hard.

The black knot fungus initially infects young growing shoots or wounded stems in spring. Spores are released from mature black knot galls and splashed by rain or blown by the wind to infect new branches. Infected branches do not begin to swell until late summer or early the next spring, and it will be one more growing season before those galls are mature and capable of releasing spores themselves.

Photo 2: Branch killed by black knot gall.
M.Grabowski, UMN Extension.

The damage done by black knot can vary greatly depending on the species, variety and intended use of the tree. Some ornamental Prunus trees can have a canopy full of galls and still produce a beautiful flower show in the spring and a healthy flush of foliage in the summer. In other trees, galls can distort twig growth and eventually girdle the twig, killing all leaves and branches beyond the gall. Multiple infections of this type eventually reduce the vigor of the tree and send the tree into decline. Occasionally black knot infections can be found on the main trunk of the tree. These infections are swollen and covered with lumpy black gall like growth. They often crack and ooze sap. Although the black knot fungus will not cause trunk decay itself, the cracks formed by a trunk infection can provide an entry point for other wood rotting fungi.

March is the best time to prune out and destroy black knot galls. Make the pruning cut 4 inches below the visible gall. This will insure that all of the fungal infection has been removed. Galls should not be left near the tree, since spores can be produced even on pruned branches. Instead remove or destroy the infected branches.

New Publication on EAB Insecticides Now Available

Jeffrey Hahn, Asst. UMN Extension Entomologist

Photo 1: Check out this new EAB fact sheet.
Jeff Hahn .

A four page fact sheet entitled Frequently Asked Questions Regarding Potential Side Effects of Systemic Insecticides Used To Control Emerald Ash Borer was recently completed.  This publication was written by entomologists at the University of Ohio State, Michigan State University and University of Minnesota Extension and reviewed by 14 specialists.  It was produced to help answer common questions people have about the insecticides used to treat emerald ash borer using the most current research based information.  As emerald ash borer becomes more widespread in Minnesota (and other areas of the country) and insecticides are considered, more people will have these questions and need access to unbiased, fact-based information.  You can find this publication at the following link.

Prunus x maackii: Amur Chokecherry Tree

Emily Dusek, UWRF

With a peeling, golden-hued bark reminiscent of the Betulaceae (birch) family, along with its dainty white blossoms dangling on two to three inch racemes from early to mid-May, it is clear the Gold Rush Amur Chokecherry Tree is a beautiful enhancement to any landscape!

The Amur Chokecherry (actually a member of the Rosaceae or rose family) calls the eastern side of the world home--specifically, Russia, Korea and Manchuria. It was brought to the United States in 1878 to the Arnold Arboretum as a gift from the Botanic Garden in St. Petersburg, Russia. Despite it's being native to the harsh taiga of Eurasia, this tree is still considered a desirable choice from zones 3a to 7. Though it's susceptibility to cherry pests (which include borers, scale, aphids, tent caterpillars, canker and leaf spot) increases in warmer climates, the Amur Chokecherry is recommended for cool northern climates where the majority of these problems are nonexistent for this species. It's a relatively trouble-free tree for the harsher climates of the world.

The Amur Chokecherry is tolerant of full/part sun and/or part shade in acidic, humus-rich, well-drained soils. While it has a tolerance for drought, it prefers to be kept moist (but not wet) at all times. On newly propagated trees, there is an occasional onion skin effect where the bark peels off on the young branches; exposing an array of colors that vary between yellow-brown, to orange-brown, to a copper color with a very glossy effect!

During the second or third year, the glabrous stems will start to develop lenticels. These branches will develop into a dense, round or broad-oval formation, spreading out to 25-35 feet in width. The Amur Chokecherry also has a tendency to grow with several trunks. Depending on what the owner desires, this tree may be grown in either clump form or as a single specimen (if trimmed to do so)! The maximum height ranges from 30' to 45.' The bark is similar to the mature branches in regards to how the colors vary from a bright, highly glossy copper to gold and amber. The lenticels are also prominent on the bark, forming long, horizontal, decorations across the thin smooth bark. As it ages, the bark will start to exfoliate in a manner similar to that of a river birch (Betula nigra).
With such ornamental bark, one might expect it to be the only positive feature of the Amur Chokecherry--but that is hardly the case! In early to mid-May, there is a lovely display of white flowers that consist of 5 petals, 3/8" in diameter. They occur in 2 to 3" long racemes that have about 20 to 30 flowers on them. The fruit then develops numerous small red drupes that are ¼" in diameter, and will then mature to black as they ripen. These fruits can be used to make jams, jellies, juice, or just left on the tree, luring birds near and far.

The dense, dark green summer foliage of the Amur Chokecherry contrasts nicely with the shiny bark. Come fall, the Amur Chokecherry is not the most exciting of specimens due to a lack of fall foliage interest, when the leaf color ranges from a drab yellow-green to an even drabber green. But when this uninteresting foliage is combined with such splendid bark and sweet little is an easily overlooked shortcoming.
The Amur Chokecherry is radiant in the winter season when its bark presents a stark contrast to the snow. Though this type of tree has multiple uses, it is most commonly used as an easily viewed specimen tree, small shade tree, or in a grouping because of its winter interest. Since this tree has such a cold tolerance, it may also be used as a container patio tree, or even as a replacement or complement to the dogwoods and evergreens so common in Christmas winter planters. Though the Amur Chokecherry is only known to be moderately tolerant of ozone pollution, it has been recommended by some sources for use as a buffer strip around parking lots and even for median strip plantings along highways!

If cold tolerance and pest resistance were the Amur Chokecherry's only attributes, it would still be considered a valuable tree. But when combined with its superior golden peeling bark and flowers, this tree becomes an ideal ornamental tree that is as close to being a 'tree for all seasons' as is possible!

The author, Emily Dusek, graduated with an A.S in Horticulture from Century College in 2009. She is currently attending University of Wisconsin-River Falls to parlay her A.S. into a Bachelor's of Science. She has also received invaluable hands-on lessons working at Farrill's Sunrise Nursery in Hudson, Wisconsin. Emily first got into horticulture as just a baby; she has been told her first birthday present was a mini wheelbarrow and watering can!

Calendar: March 1, 2011

Take time to focus on your houseplants before outdoor activities consume most of your gardening energy. Wash accumulated dust from the surfaces and undersides of leaves. Resume fertilizing if you haven't yet done so. Return low-light plants to their spring and summer locations, out of intense sunlight. Transfer plants that have outgrown their old containers to new ones that are only an inch or two larger in diameter. For plant health, be sure pots have drain holes or built-in water reservoirs.

The best time to have shade trees and fruit trees pruned is late in their dormant period, before buds start to open. If you have oaks that need pruning, be sure the job is completed by the end of the month. Pruning or wounding them during April, May of June leaves them vulnerable to developing oak wilt, a fungal disease that can kill red oaks and pin oaks within weeks and is usually fatal to white oaks and bur oaks within a few years.

Have you checked out the new UMN Extension website? Don't miss the latest news, University of Minnesota Extension's most recent statewide news releases, Ag News Wire columns, features and multimedia offerings. Find answers to your questions on the Garden page, and Ask a Master Gardener online. Bookmark these pages so they are handy for the growing season!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

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