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Extension > Yard and Garden News > April 2009

Wednesday, April 1, 2009

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.

Photo 1: Nut cluster. Lois Braun

But there are two wild species of hazelnuts that are hardy in Minnesota. The American hazelnut (Corylus americana) is widespread in the Eastern half of the United States, whereas the beaked hazelnut (Corylus cornuta) is found further north into Canada. Both species are shrubs found in the understory of the savannah or in open woods, often near the margins of wetlands. Their nuts are borne in clusters and enclosed in papery green husks. The beaked hazelnuts get their name from the beak or snout shape of this husk. The nuts of the wild species are tiny—only about the size of a pea, as compared to the size of a spherical dime for European hazelnuts. But they’re packed full of flavor, or so I’m told, since I’ve never actually tasted one… because of those dang squirrels.

Hazelnuts have a unique reproductive strategy. Like other members of the birch family, they produce their male flowers, catkins, in the fall. Catkins dangle from the branches all winter before expanding and releasing their pollen in the very early spring. (I once visited Itasca State Park in April when the hazelnuts were in bloom. I wouldn’t have noticed them at all if it had not been for all the yellow catkins at a time of year when the lakes were still frozen and the rest of the plant world still appeared asleep.) The female flowers, which don’t emerge until spring, are exceedingly inconspicuous. They look like a pin-head sized tuft of red on the tip of a leaf bud. What’s unique about them is that after pollination in April the pollen germinates and grows a pollen tube down the style and then…nothing happens for another two months! The pollen and the ovule do not fuse to form a new embryo until June, but after that the nut expands rapidly and is mature by late August or early September. The early flowering appears to be a strategy to take advantage of the optimal conditions for wind pollination in the early spring, when there are no leaves to get in the way of blowing pollen. The delay in formation of a new embryo may be because it isn’t until June that conditions become optimal for growing the nuts.

Photo 2: Hazelnut catkin. Lois Braun

The hazelnuts I am working on are hybrids between the European hazelnuts and these two native American species. The American species confer hardiness to Minnesota’s harsh winters, and tolerance to a disease that would kill European hazelnuts if we planted them here, while genes from the European hazelnuts increase the nut size. Unlike squirrels, we humans don’t have all day to shell out enough nuts to get a proper meal out of small nuts. We don’t have the teeth of a squirrel either.

Photo 3: One year old planting. Lois Braun

Why, you are probably wondering, am I researching hazelnuts in the Department of Agronomy? Isn’t agronomy about growing field crops? Yes. We’re interested in developing hazelnuts as an alternative crop for Minnesota, to add diversity to an agricultural landscape dominated by corn and soybeans.

There are multiple benefits to woody perennial crops such as hazelnuts. They require no tillage once they are established, and require much lower inputs for weed control and fertility than crops such as corn and soybeans. This reduces soil erosion and the potential for contamination of surface and ground water by herbicides, fertilizers and sediment. Low inputs also keep production costs low. Because hazelnuts are ideally suited for planting on steep slopes, in riparian zones, and other places that are inappropriate for annual tillage, they offer growers a way of making a profit from land that would otherwise be idle, at the same time maintaining or enhancing the ecological value of this land. They can be used in windbreaks, to reduce winter heating costs around a homestead; as shelterbelts, to protect livestock or crops from strong winds; as living snowfences, to reduce drifting snow along highways; or to protect sensitive lake and river shores, all while generating income for growers. We recommend planting low-growing perennial mixes of grasses and legumes between the hazelnut rows, which further enhances their value for stopping erosion, building soil organic matter, and supporting a complex and resilient ecosystem. Finally, they make great wildlife habitat, and the nuts are loved by a wide range of animals—especially squirrels.

Photo 4: Living windbreak of hazelnuts. Lois Braun

We believe that we will have no trouble marketing hazelnuts because the nuts are tasty and nutritious. They are high in protein, healthy mono-unsaturated fatty acids, and Vitamins B and E. They can be eaten straight, baked into cookies, sprinkled on salads, or ground into a peanut-butter like sandwich spread. The oil has properties virtually identical to olive oil, for use in cooking and in lotions. Some people are even talking about using it to make biodiesel fuel.

Photo 5: Hazelnuts laden with nuts. Lois Braun

So what’s the down side? Right now, the hybrid hazelnuts you can buy from a nursery are all seed-propagated. You probably know that you can’t take the seeds out of a Honeycrisp apple, plant them and get a Honeycrisp apple tree. They won’t come “true”. The way to get a new Honeycrisp tree is by grafting from another Honeycrisp. It’s the same with hybrid hazelnuts, except that you can’t graft hazelnuts because they’re multi-stemmed bushes. New shoots would keep coming up from the rootstock and overwhelm the grafted shoot.

The problem with planting seedlings is that you don’t know what you’ll be getting, even if the seeds came off a spectacular bush. Some may be as good as the mother plant, some may be better, but most will not. They’ll be as diverse as a litter of stray kittens. It is very difficult for a commercial grower to manage a crop in which plants that are three feet tall are right next to ones that are ten feet tall, or in which some nuts mature in mid-August and others in mid-September.

The objective of my research is to find methods of propagating hazelnuts vegetatively so that growers can count on a consistent crop. So far, mound layering has proven to be the best method, but it can only produce a few new plants from each parent plant, and is hard work. Hazelnut stem cuttings don’t root well, and tissue culture is expensive, at least to start. So I keep looking for better methods. Someday in the not-too distant future I hope that we can offer Minnesota growers, and homeowners, a reliable new crop.

Photo 6: The author inspecting a tall growing hazelnut.

But diversity isn’t always a problem. A home-owner picking hazelnuts for personal consumption might prefer a spread-out harvest. So if you are adventurous and don’t mind a little uncertainty, how about planting a couple of open-pollinated hazelnut seedlings in your yard. Here are some nurseries in our region that sell them:

Red Fern Farm

13882 I Ave.

Wapello, IA 52653

(319) 729-5905

Badgersett Research Corporation

18606 Deer Road

Canton, MN 55922

New Forest Farm

P.O. Box 24,

Viola, WI 54664


E-mail for a price list:

Seedlings come as small “tubelings”, which are actively growing, or as larger bare-root dormant seedlings. Seedlings grown a little longer in larger containers usually have better survival, but are more expensive. Some growers have found that they can increase the survival of the small tubelings by transplanting them into larger pots in June, keeping them in a nursery setting over the summer, then transplanting them outdoors in August or early September.

Photo 7: A little extra care is needed during the first year or two of establishment. Lois Braun

Detailed advice on growing them is available at

Although hazelnuts need a fair amount of attention during the first year or two, once they are established they require very little care. They do best on rich high organic matter soils, but can be grown on poor soils. Just be sure to test the soil and correct any deficiencies first. Nitrogen requirements are very low for the first few years and can easily be supplied from the soil or from compost. Composted manure may be all that is necessary to keep them productive once they start bearing nuts. Weed control, watering, and protection from wildlife are important during the establishment phase. If you have only a few it is easy to weed and water them by hand. Mulching reduces the need for both of these. By the third year, hazelnut roots should be deep enough that they can compete against weeds on their own pretty well. After this they should only need watering if it’s exceptionally dry or if they are on sandy or other droughty soils. Chicken wire cages are effective protection from wildlife, and can be removed after two winters.

Bushes will start producing in about their fourth year, but don’t reach full productivity until about year eight. At that time your biggest challenge will be getting to the nuts before the squirrels do! But if you don’t, take pleasure in having done your part to keep Minnesota’s wildlife well fed!

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.

Photo 1: A young visitor to the St. John's Abbey & University maple syrup operation enjoying sap straight from the tap.

Conditions for Sap Flow

Maple syrup-makers have long known that the key to sap flow is cold nights (below freezing) followed by warm days (above freezing). Only when the day and night temperatures fluctuate above and below freezing, will the trees release their sweet elixir. Maple syrup season in central Minnesota typically runs from mid-March to mid-April when the weather provides the optimal temperatures for sap flow. Although the best sap flows occur in spring, maple sap is reported to flow anytime the trees are dormant from October to late April. Sap flow stops when the buds expand and the leaves develop. Sap flow also ends if the temperature is continuously above or continuously below freezing. As a recent grade-school visitor to our maple syrup operation wisely noted, there is no sap flow when the weather is cold-cold or warm-warm, but only when it is warm-cold.


At night, when it is normally cold, there is little sap flow. In the daytime, once the temperature warms above freezing, sap flow begins. The sap flow is initially rapid and then declines during the day. The amount of sap flow is related to how cold it got during the previous night and is most directly correlated with the temperature of small branches in the canopy of the tree.

Photo 2: Brother Walter Kieffer using a modified chainsaw to tap trees in the St. John's Abbey & University sugarbush.

Maple sap comes from the xylem

Before discussing the hypothesized mechanism for sap flow, let’s address a common misconception. Since grade school we've learned that the xylem, or wood, transports water from the roots to the aerial parts of the plant, while the phloem transports sugars and other organic materials. Though true, this has resulted in the notion that sucrose-rich maple sap is extracted from the phloem – which is wrong. The sap that drips out of a tap, or spile, in a sugar maple tree comes from the xylem. In fact, this is the only time during the year when the fluid in the xylem is rich in sucrose, and is an exception to the wisdom we garnered in grade school.

Maple sap is under pressure


The fact that maple sap drips out of a tree through a spile or wound in the bark tells us that the pressure inside the tree must be greater than the pressure outside. When a pressure-measuring device such as a manometer is attached to a spile or the cut end of a branch, sugar maple stems can generate a pressure of about 100 kilopascals, or roughly 15 pounds per square inch, when the sap is flowing. Further, careful studies have shown that the flow rate of sap from a sugar maple is proportional to its internal pressure.

Photo 3: Late spring scene of tapped trees with bags in the St. John's Abbey & University sugarbush.

Maple sap flow occurs by a different mechanism than water transport

The flow of maple sap is not related to the normal process by which water is transported in the xylem during the growing season. According to the transpiration-pull model for water transport, a column of water is essentially "pulled" up through the xylem as individual water molecules evaporate (transpiration) from leaf surfaces. This works because of the cohesive property of water molecules that causes them to “stick together.” Thus, transpiration literally sucks water out of the stem creating a negative pressure, which is also called a tension, and which gives this hypothesis its alternate name of “cohesion-tension model.” Clearly this can’t be responsible for maple sap flow since: (1) maple trees lack leaves during the time period when sap flows; and (2) the xylem in trees that are transpiring and transporting water is under a negative pressure (or tension), not a positive pressure, like in maple stems during sap flow.

Root pressure does not cause sap flow


Gardeners know that grape vines pruned in the spring will bleed. Sap exudes from the cut stems due to root pressure. Root pressure occurs when water osmotically enters the core of a root and builds up pressures that can reach 40 pounds per square inch and higher. However, these pressures are not responsible for maple sap flow. A simple experiment shows why. When branches are cut from a sugar maple tree they will produce sap from the cut end. Since the branch is no longer connected to the roots, the roots can not be involved. Further, the stump of a dormant sugar maple tree cut off at the base produce little sap. Hence, root pressure is usually absent in maple trees when sap flow occurs. Further, root pressure is not temperature-dependent and doesn’t rely on alternating cold/warm periods as does sap flow. Although sap flow in maple is not caused by root pressure, it is responsible for birch sap flow. When a birch tree is tapped in the springtime it produces sap by root pressure. The sap can also be made into syrup and is a commercially-important product in some areas.

Photo 4: Sap sack ready to be collected.

Maple sap flow is caused by temperature-induced changes in stem pressure

So, if root pressure and normal water transport mechanisms are not involved in maple sap flow, what is the cause? The crucial factor is apparently related to the age-old observation that sap flow requires warm days and cold nights. Clever experiments have shown why the freeze-thaw cycle is necessary. When a cut maple branch is given a source of water and allowed to freeze, the stem absorbs water. This occurs because the internal stem pressure decreases. When the branch is warmed up, the stem exudes water as the pressure increases.


Now, let’s summarize our various observations and explain how sap flow occurs. At night, as the temperature gets colder, air bubbles in the sap contract and dissolve decreasing the pressure. This initiates a suction (tension) that draws water from adjacent cells. In turn, these cells are refilled by water absorbed from other cells and ultimately from the root. As the temperature continues to drop, water freezes inside hollow fiber cells in the xylem and in the intercellular spaces. Additional ice forms as water vaporizes from surrounding cells, much like the formation of frost on a misty winter morning. When ice formation is complete, the remaining gases in the stem are compressed and locked in ice bubbles. The next day, when the temperature warms, the ice bubbles melt and the compressed gases expand producing the pressure that pushes the sap out of the stem. Sap flow eventually slows by late afternoon when the stem pressure declines due to the evaporation of water from branches, internal leaks, and perhaps other causes.

Photo 5: The smoke and steam from the St. John's Abbey & University sugar shack.

Unanswered questions


This hypothesis explains why freezing and thawing temperatures are required and why sap flow is always followed by re-absorption of water. However, questions about the process remain. For example, experiments have shown that maple sap will only flow if the sap contains sucrose. Since the current model for sap flow is based primarily on temperature-induced pressure changes in the stem, it’s not understood why sucrose should be required for sap flow. Our current model suggests that the composition of the sap, whether it contains sucrose, glucose or other solute, shouldn’t matter. But it does. Continuing experiments will hopefully provide the answer to this mystery.

Photo 6: Autumn in the St. John's Abbey & University sugarbush.

Why maple?

Spring sap production is a relatively rare phenomenon. It occurs in the maples, genus Acer, and just a few other species. So, what it is about maple? The critical factor appears to be related to the distribution of liquid and gas in the xylem. Xylem is comprised of several types of cells including fibers and vessel elements. Vessel elements are the main water-transport cells while fibers are longer and thinner and serve primarily to support and strengthen the wood. In species that produce sap, like sugar maple and butternut (Juglans cinerea), the fiber cells are air-filled and the vessels are water-filled. In contrast, species that do not exude sap, such as willow (Salix), aspen (Populus), elm (Ulmus), ash (Fraxinus) and oak (Quercus), have gas-filled vessels and water-filled fibers.

The mysterious process of maple sap flow likely evolved as a way that maple could provide water to the leafless canopy during a freeze-thaw cycle. Fortunately for us, there’s no mystery about how to take advantage of the resultant stem pressures to make a sweet, springtime delicacy.

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.


Photo 2: Close examination of infected branches reveals yellow to orange blister like spots. Michelle Grabowski

Golden canker is caused by the fungus Cryptodiaporthe corni. Not much is known about the biology of this fungal pathogen. We do know that C. corni only attacks pagoda dogwoods (Cornus alternifolia), especially trees that are stressed from heat and drought. We also know that the fungi advances when the tree is dormant, killing any branch that it completely encircles. If the main trunk of the tree is infected, the entire canopy can be killed. In North Dakota, spores of the fungi were observed in May, when the new pagoda dogwood shoots were just beginning to grow. When these spores infect and how they start new infections remains unknown.

Luckily there are several things a gardener can do to reduce the risk of encountering golden canker and several steps to help control the disease in infected trees. Any gardeners with pagoda dogwoods should thoroughly examine the trees for golden cankers before new growth begins this spring. Infected branches should be pruned out, making the cut several inches below the line where the golden infected bark meets with purplish red healthy bark. These branches should be removed from the area and burned, buried, or otherwise disposed of.


Photo 3: If golden canker girdles the main trunk of the tree, the canopy above will be killed. Michelle Grabowski

Since golden canker seems to be most severe in stressed trees, gardeners should try to provide optimal growing conditions for any pagoda dogwoods in their landscape. These small trees typically grow in the understory of larger trees. They prefer shaded to partially shaded areas, with cool moist soils. This should be taken into consideration when choosing a site for new pagoda dogwood trees. In addition, mulching the soil around the base of the pagoda dogwood with 2 inches of woodchips or organic mulch will help keep the tree roots cool and moist. Water should be provided to the trees if less than 1 inch of rain has fallen each week during the summer months. With proper placement and care pagoda dogwoods can thrive in Minnesota’s landscapes, serving as a unique feature plant that will hopefully be golden in every way but one.

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.

Photo 1: Snow mold on a Kentucky bluegrass lawn. Bob Mugaas

Once the snow leaves, many people discover areas of their lawn covered with small to medium size, circular, light tan patches of what appears to be dead grass. In some cases these circular patches will coalesce together forming large areas of dead appearing grass. This condition is caused by fungi that grow and thrive in cold, moist (but not frozen) conditions such as that found at the lawn / snow interface in late fall or late winter. We describe these symptoms as snow mold. In home lawns, most of this tan, dead looking grass is confined to the grass leaves and has not affected the actual growing points of the plant. This allows the grass plant to begin regrowth and, literally, outgrow the symptoms. In fact, a light raking to lift up the grass foliage again improving sunlight penetration and air circulation in the turfgrass canopy will speed recovery and stimulate growth. There is no need for any fungicide application at this time of year.


Photo 2: Meadow vole tunnels and ridges on a home lawn. Beth Jarvis

Another common over winter artifact visible in the lawn after the snow leaves are narrow, twisting ridges of loose grass blades that cover what appears to be a shallow trench. This damage is caused by a small, mouse-like animal known as a meadow vole. This is not damage typical of that caused by the eastern mole. By the time the snow leaves and damage is visible, the meadow voles have left the area for more protective cover. While damage from these animals can occur in many different lawn settings, they are most common where lawns abut other natural areas, unmaintained grassy fields, vacant, undeveloped lots and the like. Most of their injury is confined to damaging the grass foliage with little injury to the grass crowns which are responsible for regrowing new grass shoots and leaves. Simply raking off the loose grass blades and any clumps of uprooted grass plants will help stimulate new growth and recovery. If there are some areas where there was extensive vole activity and much of the existing grass uprooted, releveling of these spots, perhaps adding a little top soil, followed by overseeding will quickly repair those areas. While grass regrowth in the actual trenches may be a little slower than the surrounding undamaged grass, they will catch up even with little to no overseeding.


Photo 3: Deicing salt injury to Kentucky bluegrass. Bob Mugaas

Early spring is also the time of year when injury from deicing salts used on streets, driveways and sidewalks becomes apparent. Most often, this will take the form of a rather narrow band of dead grass adjacent to those hard surfaces. Sometimes it can also appear as larger dead areas next to the ends of sidewalks or driveways where snow from the street and/or driveway was piled. Turfgrass injury is usually the result of temporarily moderate to high concentrations of deicing salt in those areas. After a few spring rains or a couple of thorough soakings from a garden hose, these areas can usually be repaired by seeding or sodding without further salt related injury or death. There are grass seed mixtures that contain a more salt tolerant grass known as Puccinella distans along with other traditional lawn grasses known to be more salt tolerant. Two of the more common varieties of Pucinella distans are Fults and Salty. They will usually be listed on the container seed label and the mixtures are often sold as grass for boulevard areas or other areas that receive exposure to deicing salts. Repair seeding can usually be done as soon as the soil has dried out somewhat and is no longer muddy and soft under foot. Be sure to lightly loosen the soil surface such that seeds can easily be incorporated into it. Prepackaged “mulches” can also be used as additional protection for the newly seeded area. Follow package directions for proper use of the particular product.

For more information about these and other turfgrass problems, check out Extension’s Gardening Information website at Click the “What’s wrong with my plant?” followed by clicking on the Turf icon.

Editor’s Note: The last two pictures are taken from the Gardening Information website from What’s wrong with my plant? under the Turf section (

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.

Photo 1: Flooding can negatively affect plants and degree of injury is dependant on multiple factors. Wendy VanDyk Evans,

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 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 if deposits are deep enough. 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 being 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.

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 practices being undertaken. 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.

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.

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.

A Brief Survey of Insecticides Available to Minnesota Gardeners

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.

Photo 1: Look for the active ingredient on the pesticide label. Jeff Hahn
The following is a list of common garden and yard insecticides that homeowners may find in stores. This is not meant as a complete list of every insecticide available to home gardeners that can be found in Minnesota but should include many of the most common active ingredients. Also, the listing of any specific trade names is not meant as an endorsement of these products but to just point examples of pesticides with a particular active ingredient.
When examining product labels, look carefully for the active ingredient which is often in small lettering. Also be sure to examine product labels carefully to be sure the plant you wish to treat is listed on it and the product is used correctly.
Lower Impact Insecticides
Bacillus thuringiensis (B.t.) variety kurstaki is a naturally occurring bacterial disease of insects. It is specific to caterpillars (butterfly and moth larvae). It is a stomach poison, killing insects after they have consumed it. It is most effective against young larvae. Examples include Bonide Bacillus Thuringiensis (BT), Hi-Yield Dipel Dust, and Green Light Dipel Dust.
Note: Bacillus thuringiensis var. tenebrionis, an insecticide effective against Colorado potato beetle larvae, does not appear to be available to home gardeners. The Bonide product Colorado Potato Beetle Beater which used to contain this active ingredient now contains spinosad.
Horticulture oils are either derived from petroleum oil, plant oils (typically derived from the seeds), or even fish oils. Oils are used to suffocate certain insect and mite eggs. It can also suffocate certain immature and adult insects, especially soft-bodied ones like aphids and scale crawlers, as well as mites. Examples include Bonide Mite-X (cottonseed oil, clove oil, garlic extract) and Ortho Volck oil spray (petroleum oil)
The active ingredient of insecticidal soap is listed as potassium salts of fatty acids. They are generally effective against small, soft-bodied insects, such as aphids. They are usually believed to affect insects by penetrating and disrupting the cell membranes. Examples include Bonide Insecticidal Soap, Natural Guard Insecticidal Soap, and Garden Safe Insecticidal Soap.
Neem and Neem Derivatives are derived from the neem tree, a plant found in arid tropical and subtropical areas. There are many compounds that can be synthesized from neem and different extraction methods can produce different products. Neem products are generally divided into one of three groups: azadirachtin-based products, neem oil-based products, and neem oil soap products. Neem can deter insect pests in one of several ways. They can inhibit their feeding, repel them, or disrupt their life cycle preventing them from successfully molting. Neem is generally effective against a wide array of insects, such as aphids, caterpillars, beetles, leafminers, and thrips. Examples include Green Light Fruit Tree Spray and Green Light Neem II.
Photo 2: There are many insecticide options on the market. Jeff Hahn
Pyrethrins are made from the ground flower blossoms of the chrysanthemum plant, especially Chrysanthemum cinerariaefolium. It is a fast-acting contact insecticide that affects the nervous system, paralyzing the insect. Some products may be mixed with a synergist, that is, a product that makes the pyrethrins more effective, although by itself it does not have any insecticidal properties. This insecticide is effective against a wide spectrum of insects. Examples include Bonide Japanese Beetle Killer and Garden Safe® Brand Rose & Flower Insect Killer.
Spinosad is produced by the fermentation of a soil-dwelling bacterium, Saccharopolysora spinosa. It is quick acting, attacking the nervous system of insects. It is most effective against caterpillars, flies (mostly leafminers), and thrips and is also reasonably effective against leaf beetles and grasshoppers and similar insects that consume a lot of foliage. Examples include Garden’s Alive Bulls-EyeTM, Bonide Captain Jack’s Deadbug Brew, and Green Light Lawn and Garden Spray.
This is a common group of related insecticides that are based on the chemistry of naturally occurring pyrethrum. They are long residual insecticides killing a wide range of pests. One of the more common pyrethroids is permethrin. Examples include Bonide Eight Garden and Home, Bonide Borer - Miner Killer, Hi-Yield Kill A Bug II, Ortho Bug-B-Gon Garden Insect Killer. Other common pyrethroids are bifenthrin, an example is Bug B Gon Max Lawn and Garden Insect Killer; cyfluthrin, examples include Bayer Advanced PowerForce® Multi-Insect Killer and Bayer Advanced Triple Action Insect Killer for Lawns and Gardens; lambda cyhalothrin, examples include Bonide Beetle Killer and Bonide Caterpillar Killer; deltamethrin, examples include Bonide Delta-Eight Granules and Hi-Yield Turf Ranger Insect Control; and esfenvalerate, an example is Ortho Bug B Gon Max Garden & Landscape Insect Killer.
Old Standbys
The following are products that were available when I started at the U of M (long ago) that can be still be found, although in some cases they are much less commonly available.
Acephate, an organophosphate, kills on contact and is also a foliar systemic with moderate residual activity. It is effective against a wide range of insects, such as caterpillars, sawflies, and leafminers. An example include Bonide Systemic Insect Control. Malathion, another organophophate, is a broad spectrum, contact insecticide with short residual. Examples include Spectracide Malathion and Bonide Malathion. Trichlorfon is another organophophate. It is effective against beetle grubs and caterpillars in turf. Examples include Hi-Yield Dylox 6.2 Granular and Bayer Advanced Lawn 24 Hour Grub Control. Carbaryl (generally thought of as Sevin), is a carbamate. It is a contact insecticide with moderate length residual. It is effective on many insects, especially beetles. However, they are not effective against aphids. Examples include Hi-Yield Carbaryl Garden & Pet Dust and Bayer Advanced Complete Insect Killer For Gardens.
Nicotinoids (Neonicotinoids)
This is a new class of insecticides. It has a similar chemistry to and is modeled after nicotine. These insecticides affect the nervous system of insects, paralyzing them. It has a generally wide spectrum of insects it is effective against. The most common active ingredient in this class is imidacloprid. It has both systemic and contact modes of action. Many products are applied to the soil while some are applied foliarly. Imidacloprid is effective against beetles, including borers and grubs, sawflies, and aphids and other sucking insects. It is not effective against butterfly or moth caterpillars. Examples include Bayer Advanced Tree and Shrub Insect Control, Bonide Annual Grub Beater, Hi-Yield Grub Free Zone, SpectracideE Grub Stop2 Once & Done, and Ultra Stop Tree & Shrub Insect Killer. Another insecticide in this class is acetamiprid. An example is Ortho Max Flower, Fruit and Vegetable Insect Killer.
This class of insecticide is represented halofenozide. It is an insect growth regulator, preventing target insects from finishing their development. It is effective on caterpillars and beetle grubs found in the soil. Examples include Hi-Yield Kill-A-Grub 0-0-7 and Spectracide Grub Stop Once & Done!
Slug Management
There are two common pesticides sold for the management of slugs. Metaldehyde is labeled around flowers but not around vegetables or other edible plants. It is generally considered to be hazardous to dogs. It is more effective during warm, dry weather. It is best to apply metaldehyde after a rain storm but when sunny weather is predicted. Examples include Hi-Yield Improved Slug and Snail Bait, Ortho Bug-Geta Snail & Slug Killer, and Vigoro Snail & Slug Killer Meal 2.
The other common pesticide for slug management is iron phosphate. It is labeled for both flowers and vegetables and other edible plants and is not considered dangerous to dogs. Examples include Bayer Advanced Dual Action Snail and Slug Killer Bait and Spectracide Snail & Slug Killer Bait.

Sharing the Harvest & Eating Local with Community Supported Agriculture

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.


What does CSA membership involve?

Photo 1: Sample of a weekly delivery of produce. La Finca CSA
Membership arrangements vary among farms. Some CSA operations deliver their food to the neighborhoods where members live, while others arrange for members to come to the farm and help make deliveries. Some CSA farms expect members to work on the farm at least once during the season while others only expect members to support the farm with their membership.
Although each CSA farm makes its own arrangements with its members and has its own expectations of them, being involved with a CSA operation always means sharing the rewards as well as the risks of farming. The rewards include: enjoying the freshest produce available, often harvested the same day you receive it; knowing where, how and by whom your food is being produced; having a direct connection with the people who produce your food; and supporting the kind of stewardship that is good for the land as well as its people. The risks include weather and pests. Though formidable for small, self-sustaining farmers, these risks are bearable when shared by a group of subscribers.

CSA’s in Minnesota & Wisconsin

Photo 2: Green beans. All-America Selections
Minnesota is fortunate to be home to a thriving Community Supported Agriculture movement. This innovative model for getting food from the field to the fork has existed in the Twin Cities area for two decades. We now have a solid, growing community of producers and consumers who are working together to develop a sustainable food and farming system. To find a CSA that works for you visit the Land Stewardship Project’s CSA directory (hot link ‘CSA directory’ to )

Selecting a CSA

Photo 3: Tomatoes. David Zlesak
While membership in any CSA includes a share of fresh produce, other factors may vary from farm to farm. You may want to use this list when choosing a farm:

  • Location: The CSA farms listed in this directory are located throughout Minnesota and western Wisconsin. You should keep in mind the driving distance when considering your level of involvement and the involvement expectations of the farm.

  • Pick-up site/Delivery Day: The CSA farms listed have various delivery or pick-up dates. Some farms will deliver your share to your door or to a common pick-up site, while others require you to pick up your share at the farm or help with share deliveries.

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  • Length of Season/Number of Deliveries: The length of season and number of deliveries vary among the farms. Most begin in May or June and run through September or October. Some farms have an optional winter delivery for an additional cost.

  • Types of Produce and Other Food Items: All of the CSA farms offer a wide variety of seasonal vegetables. Some farms offer unusual varieties. Others add extras to their standard shares. Some give members the option to buy honey, fruit, flowers, eggs, wool/yarn, meat or other specialties at an additional cost.

  • Opportunities for Involvement: Community building is an important part of the CSA approach; all farms encourage you to become involved. Most farms plan several farm events while others encourage their members to just "drop by." Some farms expect involvement in the farm as part of membership.

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.

calendar2_600.jpgPhoto 2: Buy and plant dormant woody and herbaceous stock before they start to grow very much and become injured in warm stores like what has happened to these roses. David Zlesak
Enjoy the great selection of dormant geophytes (“bulbs”) and nursery stock at local garden centers. It is important to try to purchase such material early and handle it properly. For hardy geophytes (e.g. lilies, liatris, etc.), hardy herbaceous perennial divisions (e.g. daylilies, hostas, peonies, etc.), and hardy nursery stock (e.g. blueberries, raspberries, roses, etc.) obtain and plant the dormant plants as early as possible. Planting them while they are still dormant and the ground is first workable will help them acclimate and come out of dormancy as the temperatures are appropriate. If such plants are kept in a warm store and start growing they begin to deplete limited energy reserves before being planted and tender growth within packages can easily be damaged. One can purchase such plant materials from the garden center soon after it arrives and then hold it in a refrigerator until one is ready to plant them.
calendar3_600.jpgPhoto 3: Cannas are one of the relatively few tender geophytes sold in local garden centers that are injured at temperatures below 50F. David Zlesak
There are also a limited number of warm season geophytes that are sold in garden centers as well that do not do well if exposed to temperatures below 50F. For such plants (e.g. calla lilies, cannas, and ranunculus) store them above 50F before planting. Consider potting them up and starting them indoors. This gives them a jump start on the growing season. They can be acclimated and transplanted outdoors when the temperatures warm up.

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