Yard & Garden Line News Volume 2 Number 9                                                              June 15, 2000

Features this issue: Garden Lilies, They're Grrrreat! Honeylocust Plant Bug Spittlebugs Aphids Insect and Mite Galls Another Large Mystery Insect Chlorpyrifos To Be Eliminated Grape Diseases Problems with Purple Coneflower and Black-Eyed Susan Are there Mushrooms in Your Yard? Plants On the Edge -- Native Minnesota Flora for Shorelines Phosphorus Impacts: Fact or Fiction? Editorial Notes

Garden Lilies, They're Grrrreat!
Deborah Brown, Extension Horticulturist

Asiatic lilies. Photo credit: Deb Brown

This year garden lilies are among the many bulbs and perennial plants that benefitted from our mild winter. But truth be told, garden lilies grow well here every year.

Despite the ease with which they're grown, garden lilies aren't used as frequently as they ought to be in Minnesota landscapes. They're such versatile plants, coming as they do in a wide variety of heights, flower shapes and colors, and bloom times. They're generally trouble-free when planted in a suitable location. And most are reliably hardy in zone 4; some even in zone 3.

If you don't grow lilies yet, do consider adding them to your garden. As long as you've got soil that drains well, and several hours of good sunlight, there's a garden lily for you.

Garden Lilies or Daylilies?
Before going any further, let's make a clear distinction between garden lilies (Lilium species) and daylilies (Hemerocallis species.)

Daylilies are more shade-tolerant than most "true" garden lilies. They have long, thin, strap-like leaves that all spring from the base of the plant. Their trumpet-shaped flowers are borne at the top of slender stems that also arise from the plant's base. Though people sometimes refer to daylily "bulbs," they really grow from fleshy tuberous roots.

True garden lilies grow from spherical bulbs made of overlapping fleshy scales. Easter lilies and old fashioned "tiger lilies" are typical of true garden lilies. Each bulb develops one stout central stem with narrow leaves encircling it from top to bottom. Flower buds -- sometimes as many as a dozen or more -- develop atop the stem and open sequentially, starting with the lowest and finishing with the very top bud.

This flowering pattern makes garden lilies ideal for use in bouquets and floral arrangements. You simply nip off blossoms as they fade. Meanwhile less mature buds expand and open so each stem stays attractive for quite a long time.

Types of Garden Lilies:

'Stargazer' lily. Photo credit: Deb Brown

There are two main types of garden lilies grown here, Asiatics and Orientals. Asiatic hybrids are more common, with literally hundreds of different cultivars available. A snap to grow, they're not particularly fussy about soil pH. They're also somewhat more winter-hardy than oriental lilies.

Asiatic lily flowers may be trumpet, bell, or star-shaped with the petals curving back. They come in a rainbow of colors, and may face upwards, sideways, or hang down-turned. Modern lily breeders concentrate on developing varieties with up-turned blossoms that are easier to see and appreciate. Often, they are quite fragrant.

Oriental hybrids have wider leaves and larger, more exotic looking blooms that open almost flat and star-shaped. Known for their intense fragrance and subtle two-toned color combinations, their petals are usually ruffly-edged and speckled. You may have seen stems of the very popular cultivars 'Stargazer' or 'Casa Blanca' for sale in the cut flower section of your grocery or local florist's shop.

Oriental lilies grow best in acidic soil that is extremely well-drained. You'll want to incorporate lots of peatmoss into the soil before planting them, then use fertilizer meant for acid-loving plants. Somewhat less hardy than the Asiatics, it's imperative that you mulch them really well each autumn as soon as the soil begins to freeze.

Both Asiatic and Oriental lilies bloom best in full day sunlight, but will perform well as long as they're exposed to about eight hours of direct sun. Less than that and they begin to stretch and grow more spindly, requiring staking to keep them upright. Their flower count is also reduced when they don't receive enough sunlight.

If your garden is too shady for Asiatic or Oriental lilies, try Martagon lilies. They grow and bloom just fine in lightly dappled shade. Martagon hybrids produce "turk's cap" flowers, smaller blossoms with petals that curve back giving them an almost "ball-like" appearance. Martagon hybrids are more delicate looking than either the Oriental or Asiatic lilies.

When and How to Plant:

Asiatic lilies. Photo credit: Deb Brown

Though lily bulbs are typically planted in autumn, there is no reason not to plant them in spring. In fact, you'll find garden lilies already potted up at some of the larger farmers' markets. You can keep these potted lilies on a deck or patio while they bloom, then transplant them into your garden. Or if you prefer, you can plant them in your landscape immediately, for instant color.

To achieve the most pleasing results in your garden, refrain from planting individual bulbs. Instead, plant lilies in groups of three to five identical bulbs or plants, each about eight to twelve inches from its neighbor to allow for increase and spreading over time. The tops of your bulbs should sit two to four inches below the soil surface if they're small and four to six inches below the surface if they're large. The sandier your soil, the more deeply you should plant them.

Plan to fertilize lilies each spring with a complete fertilizer such as 5-10-10. Once soils warm, they'll benefit from a summer mulch that insulates roots and reduces weed competition. Be sure to cover lily plantings with additional mulch in late autumn.

Caring for Garden Lilies as Cut Flowers:
It's easy to care for stems of garden lilies indoors, whether you bought them at the florists' or picked them fresh out of your own garden. Just follow these guidelines to keep them looking good for the longest possible time.

• Buy or pick lilies with one or two buds open or showing color and about to open.


• Fill a spotlessly clean container with lukewarm water and add floral preservative, if you have any, at half strength.


• Strip any leaves that will be submerged under water where they would rot


• Cut the stem on an angle, then place it immediately into the water and floral preservative solution. Hold the stem under water when you cut it, then move it to the vase with a bead of water clinging to the end of the stem.


• Keep the bouquet out of heat and direct sunlight, and away from bowls of fresh fruit. Ripening fruit gives off a natural gas, ethylene, that shortens most flowers' vase life.

Dealing With Pollen Stains
Have you ever walked away from sniffing lilies in the garden, only to find your nose has turned golden? Lily pollen can stain your skin or clothing if you rub against it. Warm soapy water will take take the stain off your skin, but don't make the mistake of wiping your clothes with a wet rag. It will only serve to spread and set the stain. Resist the urge to brush it off with your fingers, too. The oils from you skin will set the stain.

Here are ways to deal with pollen stains:

• Let the pollen dry on your clothes, then brush it away with a dry soft brush or facial tissue -- OR
--
• Gently dab the pollen with adhesive tape until it's removed.
• If some pollen remains, hanging the clothes in direct sunlight for two hours usually removes any traces.
• Pollen stains can also be removed from clothes by soaking the garments in an enzyme detergent.

Honeylocust Plant Bugs
Jeffrey Hahn, Assistant Extension Entomologist

Honeylocust plant bug injury. Photo credit: Jeff Hahn

A lot of honeylocusts do not look good this year. Specifically, leaves are stunted, distorted, and often have yellow and/or brown spots. Leaves may defoliate on heavily infested trees. This injury is primarily due to honeylocust plant bugs. They have been particularly abundant in many areas in Minnesota. Their high numbers may be due to the mild winter we recently experienced.

Honeylocust plant bugs hatch in early May, about when honeylocust leaves are first unfolding. Young nymphs are pale green. After feeding for about a month, they develop into 1/4 inch, oval green adults. Both nymphs and adults can move quickly when disturbed. Some people describe these bugs as large, fast aphids. However, aphids move much more slowly and are rarely as large as plant bugs. Adults lay eggs by the end of June and continue to feed through July. There is one generation each year.

In a many cases, honeylocust plant bug feeding affects only a small number of leaves and generally has little impact on the overall health of a tree. Young, recently transplanted trees and unhealthy, stressed plants are more susceptible to plant bug feeding, especially when high numbers occur. Most plant bug injury occurs early in the spring when the leaves are first expanding. Feeding at this time causes leaves to become distorted and dwarfed.

There are some instances where trees do not appear to be healthy but plant bug numbers are not high. For these trees, environmental conditions may also play a role in the generally poor appearance of honeylocusts. Although it is hard to put a finger on the exact cause, the very cold temperatures we had this spring following the unseasonably warm weather could be at least partially responsible.

So what are the options for honeylocusts now. It is border line to still treat honeylocusts for plant bugs this spring. The majority of feeding injury has already occurred. If high numbers still exist, an insecticide application would minimize any additional feeding otherwise it would be best to wait to take any action until next year.

If you experienced high numbers of plant bugs this year and are concerned about the health of your tree, monitor your honeylocusts next year and spray when plant bugs first appear (generally when the leaves are first opening). Acephate (Orthene), carbaryl (Sevin), permethrin (Eight) are effective insecticides. If you have seen few plant bugs and little damage, then just ignore the insects.


Spittlebugs
Jeffrey Hahn, Assistant Extension Entomologist

Exposed spittlebug. Photo credit: Jeff Hahn

Spittlebugs have been commonly reported the last several weeks in many areas of Minnesota. Spittlebugs are the immature form of froghoppers. They commonly feed on a variety of flowers and other herbaceous plants. To protect themselves from the environment, spittlebugs produce a frothy mass that they hide inside while they feed. Once you know what caused this whitish, bubbly foam, it's an easy insect to identify.

Spittlebugs use piercing-sucking mouthparts to feed on plants. Fortunately they are rarely abundant enough to do any lasting harm to plants. When spittlebugs are found in your garden the best thing to do is ignore them. If a gardener wishes, they can physically remove and crush any spittlebugs they find. The use of insecticides is rarely justified. Spittlebugs are not present on plants in early summer after they mature into adult froghoppers.

Aphids
Jeffrey Hahn, Assistant Extension Entomologist

Aphids on oak. Photo credit: Jeff Hahn

Aphids have been generally abundant on many different types of trees and shrubs. Aphids are small, pear-shaped, soft-bodied insects that usually feed in clusters. They are very small, ranging from about 1/16 to 1/8 inch in size. They are usually wingless and are usually green although some species may also be yellow, black, brown, violet, red, pink, or gray. They have an amazing ability to reproduce and can produce large number of offspring in a relatively short amount of time.

Look for aphids on the underside of leaves, especially along the veins. They insert needle-like mouth parts into plant tissue and feed on the sap. In many cases, there is no apparent damage to leaves from aphid feeding. In some cases, they may distort leaves, like ash leaf curl aphids.

Sometimes the first sign of aphids may be the presence of a shiny, sticky material known as honeydew. Honeydew is excess sugary material that aphids don't digest and eventually excrete. Objects under an aphid-infested tree may become coated with honeydew. Honeydew, however, doesn't harm plants, and can usually be washed off with water. In most cases, aphid feeding has little impact on healthy, mature trees and should be tolerated. If large numbers threaten the health of very young, recently transplanted trees or unhealthy, stressed trees, then aphids numbers should be reduced.

If you wish to treat aphids, first consider using insecticidal soap which effectively controls aphids and is ‘soft' on aphid natural enemies, such as ladybird beetles, lacewings, and aphid parasites. Insecticidal soap, however, only affects those aphids it directly contacts and you may need to repeat treatments. You may also consider knocking off aphids with a hard spray of water. Longer-lasting insecticides, such as acephate (Orthene) and permethrin are effective but are also detrimental to natural enemies.

Insect and Mite Galls
Jeffrey Hahn, Assistant Extension Entomologist

Hackberry nipple gall. Photo credit: Jeff Hahn

People have been finding galls on a wide variety of trees and shrubs. Galls are abnormal plant distortions which are often the result of insects or mites feeding on new plant tissue in the spring. The insect's or mite's saliva stimulates the otherwise normal plant cells to become deformed as they grow. These abnormal cells proliferate and surround the arthropod creating a safe haven for it to live during the summer. Many galls are found on leaves, although some galls can affect flowers, buds, stems and branches.

Some of the galls found in the landscape this year include maple spindle gall, ash flower gall, hackberry nipple gall, witch hazel gall (on river birch), erineum (or velvet) gall on linden, poplar vagabond gall, various oak galls, eastern spruce gall, cooley spruce gall, and a red polyp-like gall on elm.

Despite the appearance of galls, they rarely affect the health of vigorously growing trees and shrubs even when they are very abundant. If someone wants to treat a gall, it is usually to protect the tree's appearance. The best time to spray your tree varies with the specific gall you are dealing with but generally occurs in the spring as the leaves are first opening. Once you see galls, it is too late to control them for that season.

Another Large Mystery Insect
Jeffrey Hahn, Assistant Extension Entomologist

Adult elm sawfly. Photo credit: Y & G

We have had several reports of a large bee-like or wasp-like insect that has been found in the landscape. This insect, known as the elm sawfly, is a little over one inch long and is mostly a dark violet color. The first segment on the abdomen is yellow while the last two-thirds of the abdomen is reddish-brown or violet colored.

Despite its size, it is harmless to people (much to the relief of the person who described this insect landing on one of their toes). A larva gets to be 1 3/4 inch long. It is greenish with a blue and black stripe down its back. Larvae feed primarily on elm and willow but are not considered to be a landscape pest.

Chlorpyrifos To Be Eliminated
Jeffrey Hahn, Assistant Extension Entomologist

EPA notices Photo credit: Y & G

On June 8, the Environmental Protection Agency (EPA) and Dow AgroSciences reached an agreement to phase out and eliminate chlorpyrifos for nearly all household uses. Also known as Dursban (and Lorsban in agriculture), chlorpyrifos has been one of the most widely used insecticides in the U.S. Chlorpyrifos has been recently reviewed under the Food Quality Protection Act (FQPA) which applies a much tougher standard for all pesticides. This agreement effectively eliminates the use of chlorpyrifos by residents and greatly reduces its use by professional applicators.

Dow AgroSciences will begin to phase out chlorpyrifos. Home lawn and most other outdoor uses as well as crack and crevice and most other indoor uses for chlorpyrifos will no longer by produced by December 1, 2000. Sales of these uses of chlorpyrifos must stop by February 1, 2001 and retailers may not longer sell chlorpyrifos for the above uses after December 31, 2001.

For structural pest control operators, all termite control is restricted to a maximum concentration of 0.5 percent. Additionally, no post-construction use of chlorpyrifos is permitted except in instances of spot and local treatments, but these will also be phased out by December 2002. Pre-construction applications will be phased out by December 2005.

Uses that will be allowed to continue are applications to fire ant mounds, ultra low volume applications for mosquito control, applications on golf courses (with rates reduced by 75%), use in containerized baits in child resistant packaging, and non structural wood treatments (such as utility poles and fenceposts).

Grape Diseases
Crystal Floyd, Plant Pathology technician

Black rot on grape.

Downy mildew.

Powdery mildew. Photo credits: Chad Behrendt.

Black rot, downy mildew, and powdery mildew are fungal diseases that commonly infect grapes during the growing season. Black rot and downy mildew are the most serious of these diseases, causing reductions in plant growth and decreases in yields. The three diseases are caused by three different fungi, all of which survive winter in diseased plant material. Spores released the next growing season are windblown or rain-splashed to healthy plants. Spores of powdery mildew mainly infect the leaves of grapes, while black rot and downy mildew infect the leaves and fruit. Each disease causes distinct symptoms, which can help differentiate them from each other.

Black rot, caused by Guignardia bidwellii, usually occurs early in the growing season. The first symptoms are red to brown, circular leaf spots with dark borders. Fruit can also become infected. On fruit, the disease initially appears as small brown spots. These spots eventually enlarge until the entire berry is blackened and shriveled.

Downy mildew, caused by Plasmopara viticola, commonly occurs in June and July during warm, wet weather. Orange-brown blotches appear on upper leaf surfaces. White to gray fungal growth may be apparent on the underside of infected leaves. Infected fruit wrinkles, browns, and is usually covered with white fungal growth.

Powdery mildew, caused by Uncinula necator, produces white, powdery growth that is most noticeable on the upper leaf surfaces. Powdery mildew is most severe during periods of cool, humid weather at the end of the growing season.

Prevention of grape diseases starts by planting hardy varieties on suitable sites. Properly water, fertilize, and prune plants to maintain vigor. Control weeds to reduce the number of infections by lowering the humidity level around plants. Clean up all plant material, including fruit, at the end of the growing season to reduce the number of infections the following year. Fungicides may be used for preventative treatments or to limit the spread of disease to healthy plants. Captan and Bordeaux Mixture are available to manage black rot, downy mildew, and powdery mildew.

Problems with Purple Coneflower and Black-Eyed Susan
Chad Behrendt, Extension Plant Pathologist

Aster yellows on coneflower. Photo credit Beth Jarvis

Infected black eyed Susan. Photo credit Chad Behrendt.

Closeup of infected leaves. Photo credit: Chad Behrendt.

Both purple coneflower and Black-Eyed Susan suffer each year from two common diseases, aster yellows and a fungal leaf spot caused by Cylindrosporium species. Although these two diseases may infect the same plant, they cause distinctly different symptoms.

Aster yellows, probably a more familiar disease than leaf spot, causes chlorosis or yellowing of the plant, stunting, irregular growth, and distortion of the flower head. This unusual growth is often misdiagnosed as herbicide damage. Aster yellows is a phytoplasma disease that is carried from plant to plant by insects and survives winter in infected plant material.

To manage aster yellows all infected plants should be removed from the garden and destroyed. There are no chemical treatments available for aster yellows. Since the disease can also survive in neighboring weeds, it is important to maintain good weed control in and around your garden.

The second disease, broadly classified as a fungal leaf spot, may be caused by a number of different fungi. The fungus most frequently observed is Cylindrosporium. This disease, unlike aster yellows, mainly infects the leaf tissue causing random, brown to dark brown, necrotic spots. Although these spots occur randomly over the leaf surface, they are often confined by the leaf veins. This leads to irregular to geometric shaped lesions. In addition, lesions are usually most numerous on the lower leaves where humidity levels are the highest.

Leaf spot is a fungal disease that is dispersed from plant to plant by rain and wind, and survives winter in infected material (debris). To manage leaf spot, begin by removing severely infected plants and thoroughly cleaning diseased flowerbeds at the end of the growing. To minimize the spread of the disease, try to improve air circulation in densely planted beds, avoid overhead watering late in the day, and working in the flowerbed when plants are wet. Finally, fungicides may be applied to severely infected flowerbeds as a preventative treatment. Select a fungicide listed for ornamental plants and leaf spot diseases.

Are there Mushrooms in Your Yard?
Chad Behrendt, Extension Plant Pathologist

Mushrooms. Photo credit: Dept. of Plant Pathology

Recently, the Yard and Garden Clinic has received a number of calls regarding mushrooms within the home landscape. Mushrooms typically appear in the home lawn, beneath shade trees, and in decorative wood chip mulch. Varieties of shapes, sizes, and colors have been described. In addition to the typical brown mushroom with a stalk and cap, we have received a number of calls on flat, brightly colored fungal growths that later become dry and powdery. This type of fungus is known as a slime mold.

There are two basic categories of mushrooms: pathogens, and secondary decomposers. Fortunately, most of the mushrooms that fruit within the home landscape are secondary decomposers, which simply degrade organic material and fruit when conditions are wet. Thatch, tree stumps and roots, and wood chip mulch are common forms of organic material.

It is uncommon for pathogenic mushrooms to appear within the home landscape, but two common diseases that do occur within the home landscape include fairy rings in turf and Armillaria root rot of woody ornamentals. Even these two diseases are generally considered secondary in nature.

Finally, beneficial symbiotic mushrooms, called mycorrhizae, may fruit within the home landscape. These mushrooms form a symbiotic association with the tree roots enhancing the uptake of nutrients and moisture, and typically fruit beneath the canopy of the tree. It is difficult to differentiate between beneficial mycorrhizae, secondary decomposers, and the pathogen Armillaria. For an accurate diagnosis, contact a qualified professional.

Since most of the mushrooms fruiting within the home landscape are secondary decomposers, there is no need for chemical or cultural treatments. Once the weather dries or the organic matter is decomposed, the mushrooms will go away. In the meantime, mushrooms can be raked up and discarded.

Plants On the Edge -- Minnesota Flora For Shorelines
Mary M. Blickenderfer, Extension Educator--Shoreland Vegetation and Landscape

Shoreline restoration project. Photo credit: Beth Jarvis

Highbush cranberry fruit. Photo credit: Mary Blickenderfer

Highbush cranberry flowers Photo credit: Beth Jarvis

Meadowsweet. Photo credit: Mary Blickenderfer

Dogwood. Photo credit: Mary Blickenderfer

Canada anemone. Photo credit: Mary Shideler

Swamp milkweed. Photo credit: Jean Pitt

Asters. Photo credit: Beth Jarvis

Blue flag iris. Photo credit: Mary Shideler

Joe-Pye-weed. Photo credit: Beth Jarvis

Vervain. Photo credit: Mary Shideler

Golden Alexanders. Photo credit: Mary Blickenderfer

Sedge.    Photo credit: Mary Blickenderfer

Wild rye. Photo credit: Mary Blickenderfer

Sensitive fern. Photo credit: Mary Blickenderfer

A unique group of native plants that tolerate "wet feet" grow along rivers and streams, around lakes and ponds, and in wet depressions on Minnesota's landscape. These plants have evolved strategies to survive in the transition area, or ecotone, between aquatic and surrounding terrestrial regions. Starting approximately at the water’s edge, this area extends up the shore to include the area under water during the spring floods and after major rain events. Soils in the transition area are permanently or periodically saturated with water during the growing season, producing anaerobic conditions in the root zone. This creates a problem for most plants, because plant roots require oxygen for respiration. While the roots of their terrestrial counterparts find adequate air exchange in the upper 8-12 inches of soil, plants growing in the anaerobic soils of transition area (as well as aquatic plants) have been documented to "pump" oxygen internally to their roots to overcome this problem.

Plant species in the transition area tend to be relatively consistent throughout the state, influenced less by soil type than by the full/partial sun exposure, moist soil, and disturbance typical of this area. Disturbance caused by fluctuating water levels, sediment deposition, wave impact, ice thrust, and humans will affect the site-specific plant composition at this water-land ecotone.

Plants in the transition area provide several benefits to the shoreland environment. The dense, fibrous roots of native grasses and sedges stabilize the soil, reducing erosion. Woody trees and shrubs may lessen the effects of ice thrust along the shore. Removing native vegetation in this area and/or replacing it with shallow-rooted turf or sand beach may accelerate erosion. The result may be a gradual loss of shoreline, gullies, and/or undercutting of the bank’s toe followed by periods of slumping of the bank into the water. These plants also absorb nutrients during the growing season that may otherwise enter a body of water, causing excessive aquatic plant growth. In addition, shoreland plants provide critical habitat (food, cover, and/or nesting sites) to over 25 species of birds and numerous other creatures.

Some people have successfully restored native vegetation to previously developed lake and river shoreland properties and other wetland areas. Others have enjoyed creating water gardens or ponds. Yet few people truly appreciate the diversity and beauty of "the plants on the edge." Below, find a sampling of several native plants that are common to the transition areas along rivers and lakes and in wet areas throughout Minnesota. All of these have been successfully used in shoreland restoration projects and can be purchased at nurseries in our state that specialize in native plants. (Note: Installing plants below the ordinary high water level on public waters requires a permit. Contact your local DNR-Fisheries for permit information.)

SHRUBS
Highbush-cranberry (Viburnum trilobum)

Common in wet soils along lake edges, this species seem to thrive equally well under cultivation in the upland. Large clusters of white flowers bloom in early summer. By late September, the bright red berries of the highbush-cranberry attract many species of birds. This species will grow to about 10 feet in height if not browsed by deer. Protect young shrubs.

Meadowsweet (Spiraea alba)

A member of the rose family, this common shrub grows to 3-4 feet tall in low, moist, and usually acidic soil. The delicate white flower clusters at the ends of branches attract butterflies.

Red-osier dogwood (Cornus stolonifera)

A wildlife favorite found in moist soil along water margins or in other low areas, this hardy shrub can reach 8 feet in height, but usually averages only 4 feet tall where deer are abundant and keep it trimmed. Large clusters of white flowers attract butterflies and other insects in early summer. Clumps of white berries provide food for birds and other critters starting in early autumn. The bright red stems are a welcome sight against the stark, white backdrop of snow in the winter.

FLOWERS

Canada anemone (Anemone canadensis)

An attractive groundcover in both low and upland areas, this species grows to no more than 2 feet in height and spreads via underground rhizomes to form a dense cover of vegetation. Its delicate, single, white flowers bloom from late May through late June against a backdrop of dark green, deeply divided leaves.

Swamp milkweed (Asclepias incarnata)

Isolated or in small patches in swamps, ditches, and along pond and lake margins, this milkweed is easily spotted in mid-summer by its bright pink-red cluster of flowers atop a three-foot tall stem. By August, these flowers have been replaced by long, slender pods typical of the milkweed family. Like its relatives, this milkweed attracts monarch butterflies that lay their eggs on the foliage. When these eggs hatch, the striped caterpillars feed on the milkweed leaves, from which they sequester toxins that make them unpalatable to predators.

Aster (Aster spp.)

Wet meadow asters vary in color from white (Flat-topped and Marsh asters) to pale lavender (Red-stemmed aster) to intense blue (Aster novae-angliae). Each blossom appears to be one flower but is actually made up of many smaller flowers. Those flowers in the outer ring each have a 'ray' or petal attached, while the innermost flowers do not. Asters color the garden beginning in late summer and last through autumn. Plants may reach 1-3 feet in height.

Joe-pye-weed (Eupatorium maculatum)

Blooming in isolated patches along lakes and in moist ditches starting in late July, this species is an 'eye-catcher.' It stretches to seven feet under ideal conditions and has large, flat-topped clusters (umbels) of magenta flowers at its top. Preferring 'wet feet,' it has also been planted as a stunning backdrop in formal, upland gardens. According to legend, Joe Pye was a Native American herb healer.

Boneset (Eupatorium perfoliatum)

Occurring along side its relative, Joe-pye-weed, this less conspicuous species forms a smaller umbel of white flowers in late summer. Its scientific name 'perfoliatum' describes the unusual leaf-stem arrangement where the stem appears to 'skewer' the opposite pairs of leaves that are joined at their bases.

Blue flag iris (Iris versicolor)

Patches of this unmistakable purple-flowered plant ring lakes and marshes and adorn wet ditches. Several plants may arise from a single, large, submerged root system, technically called a rhizome. It blooms late June through July. The blue-green, sword-like leaves continue to provide a unique texture after flowering.

Blue vervain (Verbena hastata)

Found naturally in moist soils along water margins, this plant grows equally well in upland gardens. Several pencil-like spikes of purple flowers form a unique candelabra arrangement atop a 4-5 foot stem. The flowers start blooming from the bottom of the spike and progress upward during mid-summer, forming a ring of purple flowers at any given time.

Golden alexanders (Zizea aurea)

A member of the carrot family, plants this species produce many umbels of bright yellow flowers that begin blooming in late May and last through mid-June. This plant grows in low and upland areas.

GRASSES AND GRASS-LIKE PLANTS

Sedge species (Carex spp.)

Many of these sedge species form dense clumps at or near the water's edge. Often mistaken for grass, most sedges are conspicuous by their yellow-green leaves and unique seed heads, some of which resemble caterpillars. Ranging in height from 2-4 feet, the dense, fibrous roots of these species stabilize the soil along shorelines and the above-ground portions provide food and cover for wildlife.

Wild rye species (Elymus spp.)

These species grow in moist (Wild Rye) to drier soils (Canada Wild Rye) to a height of 3-4 feet. The seed heads of these grasses are unique and very attractive, thanks to the long, slender appendages (called 'awns') of each seed coat. Canada Wild Rye awns curl when dry to form arching tail-like seed heads which add year-round visual interest.

Manna grasses (Glyceria spp.)

These grasses grow in shallow water, wet soil, and bogs to a height of 3 or more feet. The drooping spikelets of overlapping seeds resemble the rattler of a rattlesnake, giving one species its common name (Rattlesnake manna grass). As the common name of another species (Fowl manna grass) suggests, the seeds are an important food source for waterfowl.

FERNS

Sensitive fern Onoclea sensibilis)(

This fern grows up to 2 feet tall in wet to moist soils. It spreads to form a relatively low groundcover of coarsely divided leaves. At first frost its leaves die, leaving dark brown fertile stalks standing.

Cinnamon fern (Osmunda cinnamomea)

Its elegant, vase-shaped cluster of sterile leaves reach 3-4 feet. The separate fertile leaves are a striking brown-orange color, hence both its common and scientific name "cinnamon". This fern grows in marshes, wet woods, and swamps, usually in acidic soil.

Royal fern (Osmunda regalis) Similar in occurrence to the cinnamon fern, the fronds grow to 4’ in height with the fertile portion borne at the frond's tip rather than on a separate stalk.

Phosphorus Impacts: Fact or Fiction?
Bob Mugaas, Extension Educator and Professor-Horticulture, Hennepin County

The culprit? Photo credit: Bob Mugaas

As gardeners, we are all aware of the need to be environmentally responsible in our gardening practices such that we protect our valuable soil and water resources. One of the important ways of doing that is to properly manage our plant nutrient inputs, especially phosphorus. With that thought in mind, this article will focus on the nutrient phosphorus, its use in lawn care, and its potential to create problems in our environment, most notably our water resources.

By way of review, it is important to remember that the element Phosphorus (P) is critical for the health of the plant. It is very important to the energy mechanisms in the plant and in the plant's ability to reproduce cells for survival purposes and replace those that are destroyed or damaged. Unlike the major nutrients of nitrogen and potassium which are used by the plant in relatively large quantities, smaller quantities of phosphorus are required by plants to keep them healthy and functioning. Because of the critical requirements for phosphorus, it is important that plants have adequate availability of soil phosphorus. Fortunately, many of our soils already contain medium to large amounts of phosphorus, a small portion of which is generally available for plant use. This often makes the need for adding additional phosphorus through fertilizer applications unnecessary.

It is also important to remember some key points about how plant nutrients move in (or over) our soils and consequently their potential to move offsite and create pollution problems. The two most significant ways for plant nutrients to move via a water pathway in our environment is through leaching and runoff. Leaching is the movement of water vertically down through the soil. As it does so, it can carry nutrients and in some cases very tiny soil particles. Of our plant nutrients, nitrogen is the most vulnerable to this kind of soil movement. Nitrogen can be lost from the rootzone of the plant through leaching and potentially contaminate groundwater resources. Because of the chemistry of phosphorus and its ability to interact with soil minerals and other soil elements, it is bound very tightly and quite resistant to leaching. As we shall see, P can be readily lost in runoff water.

Runoff involves the movement of water laterally across the site. Assuming a bare soil surface, the faster the runoff and the greater the runoff volume, the more likely it will carry soil particles, surface debris and soluble materials off the site and potentially into surface water areas. As soil particles move in runoff, it is very likely that some phosphorus bound to those soil particles will move with them. Phosphorus can then disassociate from the particle or remain bound to it throughout its journey to the nearby waterbody. For example, once entering a lake it may remain bound to the soil particle and settle out as sediment on the lake bottom or enter into solution free to move about in the main water body. It is the latter situation that can cause significant algae blooms turning the lake pea soup green and greatly reducing the water quality.

Image credit: Bob Mugaas

Recently, there has been a great deal of public and political interest in prohibiting the use of phosphorus containing fertilizers on lawns. Before, making a judgement about whether that is good or bad policy, let's consider the extent to which this may even be a problem. First, there is often a perception that goes something like "what goes on a lawn, runs off a lawn". Again, remember that the thousands of individual grass shoots that make up a healthy lawn form a very difficult path for any liquid, including water, to move through them. By slowing the speed of water flow across this surface, you allow more time for water to infiltrate into the soil long before it ever reaches a curb or other hard surface where it can readily move into the storm sewer system.

A wide array of research done at various Universities around the country, indicates that only under intense storm events where rainfall rates of several inches per hour coupled with sufficient slope do we see any significant runoff from that lawn surface. It has also been shown that compared to bare soil or thin turf areas, a healthy, dense lawn that provides 100% soil cover improves soil porosity over time and thus aids water infiltration into the soil. Runoff occurs only after the rate of soil infiltration has been exceeded. In comparison, a hard surface such as a street gutter or driveway, provide virtually no infiltration and runoff is almost immediate from those surfaces. Therefore, a healthy lawn area can provide a substantial benefit in controlling the amount of runoff from a particular site. Runoff from water saturated soils will occur more quickly than those not already waterlogged. While it is intuitively reasonable that runoff should occur more quickly from compacted soils underneath a lawn surface, the research regarding this is somewhat inconclusive.

When runoff from a lawn surface does occur it is likely to carry some amount of P with it, either in the organic form or inorganic form. Organic forms of P are generally quite soluble and therefore can move quite readily with water flow. Organic forms are derived from decaying vegetation in the lawn such as clippings, dead shoots and other plant parts, tree leaves and some organic fertilizer products. Inorganic forms are those where P is not combined with carbon as part of the molecular structure. The inorganic forms are commonly associated with most of the non-organic fertilizer formulations or they can arise from decomposition of the organic forms where P is released into the soil solution and can be available for plant uptake. Phosphorus is usually taken up by the plant in its inorganic forms of primary and secondary orthophosphate.

Clippings in street. Photo credit: Bob Mugaas

Second, some studies have observed that when additional P is added to lawn areas already high in P, runoff, when it occurred, did show higher levels of P than those lawns high in P but with no additional P fertilizer added. The point of these investigations was to help answer the question as to whether or not additional P applied to soils already high in P was problematic. Results from this work suggest that it could be. However, additional investigation is needed to help verify these initial results and perhaps help clarify some of the questions about P reactions and interactions in soils where its levels are already very high.

Third, lets go back to the structure of our lawn surface. Remember, it is a highly, tortuous path for any liquid trying to move over it. Again, all the grass shoots present on the surface of a healthy, relatively dense lawn provide a great deal of interference to any water trying to move through them. Because of that resistance, it would seem that movement of any length down even modest sloping areas would be very minimal.

Hmmmm! That poses a very interesting question. How far and how quickly does water move through a healthy, dense lawn surface? In other words, does water during a rain or storm event travel long distances down a sloping lawn area or, do the grass shoots help trap, slow and diffuse that water droplet as it hits the lawn area? The latter would likely result in minimal movement of that water and very likely prevent any long distance movement. Given that it takes a relatively intense rainfall event to initiate runoff from a lawn surface, one might speculate that our lawns our very effective at diffusing the impact of water droplets and minimizing the amount of runoff from a site. Unfortunately, more definitive answers to that specific question will have to wait further investigation.

Runoff as affected by turf density. Image credit: Bob Mugaas

Runoff from lawn areas may be more of an issue in the 1 or 2 feet adjacent to curbs, driveways, sidewalks or other hard surface areas where our lawn grasses often perform poorly, especially during the hot summer months. Due to the often, less vigorous, thinner turf in these areas there may be a disproportionate contribution of contaminants including P from those areas. Therefore, the majority of lawn runoff may only be contributed from a relatively small area where the grass isn't as healthy or dense rather than from the entire lawn area. Again, further research is needed to more fully assess these situations and their contribution to lawn runoff.

Finally, one further line of evidence has to do with the application of nitrogen fertilizer. Most of us have probably experienced a time when we were not very careful to fully overlap an application of lawn fertilizer containing nitrogen. A few days later, evidence of our carelessness is expressed as skipped areas where the lawn is distinctly more yellow green than a healthy darker green color. Remember, these fertilizer particles are dropped down into the same bunch of grass shoots that our water is trying to move through when it rains or is irrigated. At the lawn surface there is also debris from grass clippings as well as other dead and dying parts of grass plants that help trap and protect that fertilizer particle from moving.

If water were moving through the grass with any velocity at all, one would expect that these tiny particles would be moved around and carried away from the place where they were originally deposited. However, the symptoms that we see associated with skips in fertilizer application are very distinct with relatively sharp lines of demarcation between fertilized areas and unfertilized (skipped) areas. These skipped areas can be as little as a couple of inches and still be quite visible even on sloping areas. If there was lots of fertilizer particle movement following rainfall or irrigation, the nutrients would be moved around and any real visible distinction between fertilized and unfertilized areas would be blurred at best. Again, if this were true, we could be somewhat careless in our application and the nutrients would still move around to cover our skips. However, that is not what we observe.

Uneven fertilizer application. Photo credit: Bob Mugaas

The debate on whether or not to ban or severely restrict phosphorus-containing fertilizers for use on lawns will be continued. Need for additional P can easily measured through the use of a soil test. Therefore, we have a decision making tool when it comes to adding additional P or not. If it is not needed, then lawn fertilizers containing no P can and should be used.

However, it is also important to recognize that our lawn grasses, kept healthy and growing vigorously are a plant material system that can contribute positively to surface water quality. Let us be careful to not fault the plant material for contributing to degraded water quality when poor management practices are the real culprits. There is not much we can do to change the genetic characteristics of the grass plant. There are many things we can do to make sure our lawn management practices and landscaped areas are as environmentally responsible as possible.

Editorial Notes

Brisley locust-- Robinia hispida Photo credit: Beth Jarvis

Robinia hispida is just about done blooming in the Twin Cities. I love the plant--in a neighbor's yard, several blocks away. It's a native suckering shrub, hardy to USDA zone 4a, that can reach 12'. It fixes nitrogen, because it's a legume, setting its brown pod fruit sparingly. It's tolerant of pollution, salt and drought heat. Unfortunately, it's also susceptible to several diseases and insect pests and can break up in an ice storm due to brittle wood. Oh, and all parts are supposedly poisonous.

In our July 1st issue, Bob Mugaas will continue his phosphorus discussion but focusing on water quality issues. This summer, Dr. Carl Rosen, who wrote about soil tests in the May 15th issue will continue the discussion to include pH and soluble salts; Dr. George Heimpel will discuss Intergrated Pest Management as it applies ot the home garden and Dr. Cindy Tong, our post harvest specialist, will talk about handling garden produce.

I rely on your comments and questions for ideas for future articles. Please, keep the story ideas coming! We really try to be responsive to your needs.

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Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. Katherine Lanpher hosts the program that is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

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Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator

Websites
Sustainable Urban Landscape Information Series. This site contains everything from landscape design planning and lawncare to both herbaceous and woody plant selection databases. The URL is:http://www.sustland.umn.edu


For pesticide info, for both home owner and professionals, check out:

http://www.crc.agri.umn.edu/~mnhelps/

There's also some very interesting reading at Forest Products website. To get there from here, click on: http://www.cnr.umn.edu/FR/extension/

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