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April 2009 Archives

What's up with that?!

David C. Zlesak


If you are getting tired of long, cold winters you are not alone. The skunk cabbage (Symplocarpus foetidus) generates its own heat (thermogenesis) come late winter/early spring and starts growing. Emerging spathes (modified leaves) contain floral organs and they can melt their way through the snow and ice. Stored energy is used to produce heat and warm growing tissue. This process occurs for up to two weeks and while this is happening temperature in such tissue is well regulated and is typically 36F above the ambient temperature! Why do skunk cabbages do this??? The answer is to attract pollinators. Early emerging insects are drawn to the warmth of these early flowers as well as the unpleasant, carrion-like scent that they emit.

Photo 1: Joseph O'Brien, USDA Forest Service,

Hazelnuts in Minnesota?

Lois Braun, University of Minnesota Research Fellow


When I tell people that I am a hazelnut researcher in the Department of Agronomy at the University of Minnesota, they invariably respond in one of two ways. They may say, “Oh! I didn’t know that hazelnuts grew in Minnesota!” Or they may say, “We used to pick wild hazelnuts in the woods when I was a kid—but we didn’t usually get very many because the squirrels got them all.”

More on squirrels later.

People are right that European hazelnuts, Corylus avellana, the ones that produce those big round nuts you find in party nut mixes, don’t grow in Minnesota. They’re not winter hardy here, at least not the domesticated varieties, which come from the Mediterranean region of Europe. In this country they’re grown in the Pacific Northwest, mostly in Oregon.

The Mystery of Maple Sap Flow

Stephen G. Saupe, Ph.D., College of St. Benedict/St. John’s University
Biology Department, Collegeville, MN 56321, (320)363–2782;


An annual springtime event from Maine to Minnesota is the production of maple syrup. Each spring, syrup-makers head to the woods to collect sap from the sugar maple tree (Acer saccharum Marsh.) and then cook it into one of nature’s greatest gifts. Although this ritual has been practiced for many years since its discovery by Native Americans, surprisingly the actual mechanism responsible for sap flow is still something of a botanical mystery. So, exactly what do scientists know about why sap drips out of a sugar maple tree in the spring? To answer this question we must first understand the conditions that affect the flow of maple sap, since our final explanation must account for these observations.

Golden Canker on Pagoda Dogwood

Michelle Grabowski, University of Minnesota Extension Educator


The word golden brings about images of wealth, vitality and prosperity. Unfortunately when this word is used to describe the branches of a pagoda dogwood, the connotation is quite the opposite. Golden canker is one of the most common diseases of pagoda dogwood small trees/large shrubs in Minnesota and it can be disfiguring and even deadly.

Photo 1: Yellow infected branch areas contrast sharply with purplish red healthy bark. Michelle Grabowski

In the early spring sunlight the infected branches are bright yellow to orange compared to the dark almost purplish red healthy bark. The striking contrast is almost pretty. Sadly any branch that has completely turned yellow is already dead and will not leaf out this spring. Close examination of these yellow branches will reveal that the branch is covered in tiny blister-like orange spots. A sharp line marks the border between healthy and diseased branch tissue.

Early Spring Lawn Care Tips

Bob Mugaas, University of Minnesota Extension Educator


While the first few warm days of spring seriously tempt one to get out and do something in the yard and garden, patience may be the better virtue. One of the first tasks many people want to do is rake the lawn. Raking is a good idea as it helps to loosen matted down grass, thereby allowing sunlight and air to reach the soil surface. In turn, this helps warm the soil and stimulate grass into active growth. However, trying to do this too early when soils are still cold and muddy will unnecessarily uproot many healthy grass plants and contribute to increased soil compaction. Hence, the gardeners rule of thumb, stay off and avoid working in or on wet, muddy soils, applies equally well to lawns as it does to gardens. When the soil begins to dry out and is no longer soft and muddy under foot, that’s soon enough to attempt raking a lawn. Each lawn will be a little different in how quickly it starts to warm up and dry out. Monitoring your lawn’s condition every few days early in the spring will determine when its okay to be walking on it and raking can begin.

Repairing Spring Flooded Lawns

Bob Mugaas, University of Minnesota Extension Educator


In the early spring before lawns begin active growth (i.e., foliage is still mostly brown) and the ground is still thawing, 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.

Jeffrey Hahn, Asst. Ext. Entomologist
Now that we are leaving the doldrums of winter behind us, the promise of a new growing season beckons and we can start preparing to work in our gardens and landscapes again. Although we hope we don’t encounter insect pests, we should be prepared to act if it becomes necessary. When using integrated pest management (IPM), we explore any non-chemical methods that could be effective first. However, there may times when some of us may need to consider applying an insecticide in our garden or yard.

Text and sketch below used with permission from the Land Stewardship Project
*Ideas and wording used taken from MACSAC, the Madison Area Community Supported Agriculture Coalition.


What is Community Supported Agriculture (CSA)?

CSA farms provide a regular delivery of sustainably grown produce (often weekly or every other week) to consumers during the growing season (approximately June to October). Those consumers, in turn, pay a subscription fee. But CSA consumers don't so much "buy" food from particular farms as become "members" of those farms. CSA operations provide more than just food; they offer ways for eaters to become involved in the ecological and human community that supports the farm.

Garden Calendar for April

calendar1_600.jpgStop pruning Oaks. April, May and June are considered high risk months for Oak Wilt infections. At this time the fungal pathogen is producing spores that can be carried by beetles from the Nitidulidae family. These beetles are sap feeders and will be attracted to fresh pruning cuts on oak trees.

Photo 1: Do not prune oak trees during April-June to avoid oak wilt infection. David Zlesak

There is still time to start seeds of fast growing warm season flower and vegetable species indoors for outdoor transplanting after danger of frost. These plants include: cosmos, marigolds, tomatoes, and zinnias. Cold hardy annuals can be direct seeded in the garden during April and include: calendula, sweet peas, peas, and larkspur. Cold hardy annual transplants we have started ourselves or purchased from the garden center can also be planted and include vegetables like cole crops (broccoli, cabbage, cauliflower, etc.) and flowers like pansies, snapdragons, and stocks.

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