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August 2009 Archives

Farewell and Hello

Thumbnail image for David Zlesak Dear Yard and Garden News readers,

I am resigning from the University of Minnesota Extension to start a new  position just across the border at the University of Wisconsin-River Falls (UWRF) as an assistant professor in Horticulture.  Leaving the University of Minnesota Extension is bittersweet because I truly love Extension and all the wonderful people I've gotten to know and the opportunities I've been very fortunate to be a part of.  The Yard and Garden News is one of them- first as a frequent author and then also as your editor.  I have loved interacting with those of you that have contacted me and the great fun it has been being on the lookout for additional authors that have interesting information and stories to share with us. At UWRF I'll have a teaching appointment working with undergraduate students.  I'll be teaching plant propagation, woody plant identification, introduction to plant science, nursery management, and hopefully also plant breeding.  I look forward to helping lay a strong foundation in our next generation of horticulturists and helping students connect to their unique passions within horticulture. 

UMore Park gazebo and annual flower bedsJoin Dakota County Master Gardeners and the University of Minnesota for a night of outdoor festivities at their 9th annual open house on Thursday, August 20th from 4 - 8 pm at the Dakota County Master Gardener Education and Research Display Gardens in UMore Park, 1605 West 160th Street in Rosemount.

Stroll through six acres of colorful educational and display gardens created and maintained by Dakota County Master Gardeners. Enjoy live music featuring steel drums while sampling wines created from the University of Minnesota grape introductions, free lemonade and fresh-cooked corn-on-the-cob, and assorted other treats for purchase. Bring in plant samples for analysis at the Plant Health Diagnostic Clinic, attend a Master Gardener mini-class on native plants, raingardens, herbs, plant propagation, or wildflowers for Minnesota, and visit interactive exhibits to learn about cow, turkey, honey bee, and other University of Minnesota agricultural research projects. Don't miss the University of Minnesota Raptor Center's live showing of native raptors such as owls, hawks, and eagles, or the wildlife exhibits from the DNR and Bell Museum. Check out the University of Minnesota Dairy and Meat Labs, the Chemopreventive Café, and the Historical Society. There will also be Junior Master Gardener activities for the children, horse demonstrations, and an appearance by Goldy Gopher.

Getting Hydrangeas to Turn Blue

David C. Zlesak and Gail Soens, University of Minnesota Extension Educator and Bailey Nurseries New Variety Coordinator / Section Grower Bud and Bloom Hydrangeas & Roses

Blue hydrangea in landscapeWith so few true blue flowering shrubs for our landscape, it is no wonder so many of us are drawn to the beauty of blue hydrangeas! Only one species of hydrangea we commonly see for sale and in our northern landscapes include cultivars that can be coaxed to bloom a true blue or, if desired, a pure pink. It is Hydrangea macroplylla which is also known as the bigleafed hydrangea. Endless Summer® is the most common cultivar of this hydrangea we see for sale in the north as it is able to bloom off of both old and new wood. This is unlike most other H. macrophylla cultivars which bloom on only old wood. Since this species is marginally stem hardy in zone 4, having the ability to bloom on new wood allows it to still flower in our climate even if the plant dies to the ground and needs to regrow from the base.

Cherry Prinsepia

Kathy Zuzek, University of Minnesota Extension Educator

Princepia Kathy ZuzekCherry prinsepia (Prinsepia sinensis) is a little known shrub native to Manchuria that has been in cultivation since 1896.  It is a member of the enormous Rosaceae family, and close relatives of prinsepia that  you may be familiar with are woody ornamental and fruit varieties from the genus Prunus (cherries, peaches, plums, apricots, almonds) and pearlbush (Exochorda serratifolia).

Cherry prinsepia is one of the first shrubs to leaf out in spring, providing some welcome color after a long Minnesota winter.  Bright green leaves are alternate on current season's growth but are produced in clusters on older wood.  A thorn is found at the base of each leaf or cluster of leaves.  The small immature leaves are soon masked by an explosion of light yellow 5-petaled flowers on old wood in late April.  In Minnesota, cherry prinsepia blooms at the same time as flowering almonds (Prunus triloba var. simplex).   

Sad Glads

Michelle Grabowski, University of Minnesota Extension Educator

Glad Fusarium wilt. Michelle GrabowskiThis time of year gladiolus blossoms are a welcome sight, whether left in the garden or brought inside as a cut flower. Unfortunately not all gardeners will have gladiolus blossoms this year. A corm rot disease of gladiolus, known as Fusarium wilt has been found in Minnesota. This disease is caused by the fungus Fusarium oxysporum f.sp. gladioli. The last part of the fungus's name 'f.sp. gladioli' indicates that this fungus has a very narrow host range and will only cause disease in gladiolus and very closely related plants. This is good news for gardeners who have infected gladiolus plants mixed with other flowering annuals and perennials.

Gladiolus plants infected with Fusarium wilt are often stunted and do not produce flowers. The leaves first yellow, then turn completely brown and fall over. The fungus infects the corm of the plant, often starting at the basal plate where the roots attach. Gardeners may see dark spots on the outside of infected corms. When cut open, a reddish brown rot can be seen within the corm.

Bird Mites

Jeffrey Hahn, Asst. Extension Entomologist

northern fowl mites. Jeff HahnBird mites, especially the northern fowl mite, Ornithonyssus sylviarum, have been a common problem this summer entering homes and biting people. Bird mites are a major pest of chickens but will also parasitize many wild birds, such as pigeons, sparrows, starlings, and robins and are associated with nests that are built on or in homes and other buildings. Bird mites normally remain on birds and in nests throughout their lives where populations can grow to the tens of thousands.

If the mite populations become too large, or if the birds abandon their nest or die, the mites will move off en masse and look for an alternate food source and commonly enter homes. Bird mites are flat and the size of a pin-head, about 1/32 inch long. Although, they are very small, people can just barely see these mites. It also helps to see them when there are a lot of them around and they are moving.


survey image Greetings Yard and Garden News readers!

First, thank you for your thoughtful responses on Y&G News' first ever reader survey. We were pleased to get so much positive feedback, and we have spent a lot of time discussing your comments about ways to make Y&G News even better.

The survey told us loud and clear that you value the timeliness and trustworthiness of the information, as well as the fact that it is Minnesota-specific. These things are important to us, too.

The survey also told us that many of you would like a shorter newsletter with postings more often, and that you would like a way to interact with the information and the educators.

In response to this, we have made the move from the one-way communication of our old webpage to the interactive options made possible with a blog. We want to stress that this new format still has the same quality information you've come to depend on. But now you can comment on the articles and take advantage of the RSS feed. It will also allow us to post more frequently.

We encourage you to explore these new features, or you can sit back, relax and read Yard and Garden News like you always have: This transition does not require any specific action from you. You will continue to receive emails from us, on the same schedule you're used to. You can easily see the lead in for the various articles and click to continue reading those you would like to. You can still click on photographs to view larger images. Photo captions can be viewed by placing your curser over the image.

Thank you,
David C. Zlesak and the Yard & Garden News team






What's Up With That?!

AARS entry 09R408This is sure a unique rose with its purple-red petal bases!! It is the new All-America Rose Selection (AARS) floribunda entry coded 09R408. Why haven't we seen this dramatic petal trait before in the roses at the local garden center? The answer is that this trait has been very difficult to bring it into modern rose cultivars and is coming from a source other than rose. One of rose's closest relatives, Hulthemia persica, is the source. Over the past 30+ years dedicated breeders have painstakingly made crosses between this wild rose relative and rose and then have made repeated backcrosses to rose.  The backcrosses to rose have been to gain more rose characteristics while still trying to retain the attractive red petal bases. Hulthemia persica is native to the region once part of the old Persian empire. It is typically found growing in very dry areas and has been difficult to cultivate in typical garden settings due to relatively high humidity and soil moisture compared to where it is native. It is different than rose (Rosa) in that it 1). does not have the two pointed paired stipules at the base of the leaf where the leaf attaches to the stem, 2). has only a simple leaf with one leaf blade rather than a compound leaf with multiple leaflets, and 3). it has a deep red blotch at the petal base. Hulthemia persica typically has rich yellow petals with deep red blotches.

Laci High, University of Minnesota Graduate Student

PJM Rhododendron is well-adapted in Minnesota. David Zlesak

After a long, dreary Minnesotan winter, gardeners anticipate and appreciate the beauty of spring flowering shrubs such as rhododendrons and azaleas (genus Rhododendron) which can be the first sign of color in many landscapes.Due to its great soil adaptability and ease of cultivation compared to other members of the genus, PJM hybrids can be found along most residential streets in Minnesota.  These plants are loaded with lavender-pink flowers nestled among inconspicuous, scaly leaves.  Even though PJM hybrids have proven to be reliable performers for home gardeners, they lack the color range and glamorous trusses of broad-leafed forms typically found in more moderate climates.

Helping Lawns Cope with Summer Stresses

Bob Mugaas, University of Minnesota Extension Educator

Irrigation can help reduce drought stress. David Zlesak.

Each summer, temporary periods of hot, dry conditions commonly occur in this part of the country.    Each summer these conditions prompt many questions about caring for and watering our lawns (as well as other landscape plants).   Following are some lawn care tips to help cope with these dry conditions during Minnesota summers.

1.  Where lawns are maintained in an actively growing condition, keep mower heights of cut between  2.5 to 3.0 inches  to encourage deeper rooting.  The cool season lawn grasses common to this area have naturally shallower, less robust root systems during the middle of the summer compared to the spring and fall periods of the year.  Shorter mowing heights without an accompanying increase in water can make that situation even worse and unnecessarily stress the plants.

Michelle Grabowski, University of Minnesota Extension Educator

Thumbnail image for Elm trees infected with bacterial leaf scorch often have a clear yellow line separating the brown scorched leaf edges from the green center of the leaf. B.Olson OK State University, NPDN .Bacterial Leaf Scorch (BLS) is a disease of shade trees common in the southern states and known to occur as far north as Ontario and as far west as Texas. To date, however, it is unclear if this disease occurs in Minnesota and how common it might be. It may seem unusual that a disease of a large tree might go unnoticed for years, but many states, having never reported Bacterial Leaf Scorch previously, have found multiple infected trees once scientists began looking for the tiny bacterial pathogen. Recent reports show that BLS is becoming more common in northern states like New Jersey. Scientists now want to know, does BLS occur in the upper Midwest?


The reason that BLS can slip by unnoticed is that the symptoms it causes look very similar to the symptoms caused by several other diseases and by environmental stress. Scorch is the term used to describe leaves that have singed brown edges. In shade trees infected with BLS, the margins and tips of the leaves turn brown. Unfortunately leaf browning at the edges and tip of the leaf is also commonly seen in trees stressed from drought, compacted soil, restricted root growth, salt damage and many other factors. In addition, diseases like oak wilt and Dutch elm disease can cause browning of leaves that may be confused with BLS. In the end, scientists rely on several laboratory tests, like ELISA, PCR and electron microscopy, to determine if BLS is truly present or not.


One Cool, Interesting Insect

Jeffrey Hahn, Asst. Extension Entomologist

Mantidfly. Jeff HahnSeveral people reported recently finding a small, ½ inch long, insect that resembles a preying mantid and a paper wasp. This unusual looking insect is known as a mantidfly. It looks like a preying mantid because of its large, front legs which are modified for grabbing prey. Mantidflies are commonly reddish brown with yellow with wings that are half brown along the front margin half and clear. Although they may not be frequently seen, mantidflies are reasonably common in Minnesota.

Mantidflies commonly parasitize spiders while other species lay eggs in the soil where the larvae prey on scarab beetle grubs, noctuid moth larvae, or social wasps. Adults feed on small insects they capture. Mantidflies are common on foliage in wooded areas during summer. People have generally found these insects outdoors but in at least one case a mantidfly was found that had accidently entered a house. Fortunately, these insects are harmless to people. If you should find one in your home, just release it outdoors.

Be On the Watch for This Elm Insect

Jeffrey Hahn, Asst. Extension Entomologist


Elm flea weevil. Jeff Hahn.The European elm flea weevil (EEFW), Orchestes alni and it's damage, was found on the University of Minnesota St. Paul campus during July.  It was found by Dr. Curtis Young, an extension entomologist at Ohio State University.  This invasive insect, common throughout Europe, was first found in the U.S. in 1982.  It wasn't found in the Midwest until 2003. It was first found in Minnesota in 2007 when an adult was collected on the St. Paul campus.


The adult EEFW is small, 1/10 - 1/8 inch long.  It is reddish brown with black spots or dark brown to black, with a long, conspicuous snout and large back legs which allows it to jump.  This weevil feeds on Siberian elm, Chinese elm, and hybrids with Asian parentage.  It rarely feeds on American elm.


EEFW overwinters as an adult and becomes active in the spring.  It moves to elm and feeds on the underside, windowpaning small areas, i.e. feeding on the lower surface of leaves but not chewing through.  A thin, opaque layer of leaf tissue remains.  Eventually, this chewed area dries up and fall out.  Don't confuse this injury with elm leaf beetle feeding which chews small oval holes in the leaves with the edge of the holes remaining green.

Garden Calendar for August

Contributor: David C. Zlesak, University of Minnesota Extension Educator

Water bags are a great tool to apply water to newly planted trees as it allows the water to slowly penetrate the soil instead of running off. David ZlesakAlthough most of Minnesota has received some rain recently, we are still well below average for the year.  Continue to water plants as needed.  Containerized plants and recently transplanted trees, shrubs, and herbaceous perennials have limited root volumes from which to draw mo isture and needed to be checked frequently for their need of supplemental water.  For most situations it is best to water deeply and thoroughly less often than providing frequent shallow water applications that don't penetrate the root zone.





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