Yard & Garden Line News Volume 2 Number 17                                                              October 1, 2000

Features this issue: Protecting Marginal Plants Look for Minnesota Gardening Calendar Buckthorn Control Swarms of Winged Ants Check Your Houseplants for Insects Cut Back Iris After Frost Use Integrated Approach To Control Fleas Snow Mold on Turf: Prevention is the Key Fun Fact: Fall Blooms On Spring Flowering Trees Editorial Notes

Protecting Marginal Plants
Deborah Brown, Extension Horticulturist

Buddlea. Photo credit: Deb Brown

As people master the art and science of gardening, they're always looking for new challenges. They're unwilling to accept some of the restrictions we face, gardening in this climate zone (zone 4 in the metro area). These gardeners are ready and willing to " push the envelope," planting shrubs and flowering perennials that normally aren't considered hardy here.

Cold-climate gardeners have always grown tender roses. Over the years they've come up with a number of ingenious ways to carry those roses through harsh winters. But what about other tender blooming plants such as buddleia (butterfly bush), Rose of Sharon (a woody member of the hibiscus family) or 'Nikko Blue' hydrangea?

Of course, the success of these efforts -- like the ability to coax hybrid tea roses through winters that drop to minus 38 degrees -- depends on several factors. Not the least of these is the mildness or severity of the weather.

Though extremely cold temperatures are far from desirable, unseasonably warm weather is no better! In our climate it's not unusual to go through one or two mini warm spells in January or February. Though most people love those little breaks from winter's cold, they can pose a serious problem to plants in gardens and landscapes.

Snow (along with fallen leaves) is Mother Nature's method of protecting plants from extreme cold. The more we get, the better. Because it's light and full of air, snow insulates well and forms an excellent mulch -- if only we could count on it.

Short-lived "tropical" interludes melt the snow, exposing soil and plants, rendering them vulnerable to the plummeting temperatures that inevitably follow. It's similar to what happens in early spring. Those few warm days begin to bring plants out of dormancy, then without warning, cold temperatures may zap them again. This is why applying a thick layer of mulch -- even to hardy plants -- is so important.

While you can't control the weather, you can choose your method of winter protection for tender or marginally hardy plants. "Mounding" is a time-honored way to care for roses here; it's relatively simple and easy to do. It ought to work for several other woody plants, too.

Key to whether a tender or marginally hardy shrub can be mounded and go on to bloom successfully is the question of when its flower buds are formed. Some woody plants make flower buds on new growth each year while others depend on buds that were formed the summer before. Growing plants that bloom on new wood is more likely to meet with success than plants whose flower buds must be protected over winter.

Mound roses in mid-October, before temperatures drop to the low 20's at night. Cut your rose back to about 18 inches and spray it with an all-purpose fungicide. Once it dries, mound soil over it. You need to cover the center of the plant to a height of about 10 or 12 inches. Add another foot of marsh hay or leaves over the mound of soil, and some chicken wire to secure it against wind. Pine boughs laid over mulch will give added protection and help trap more snow. Don't cover the mound with plastic; it prevents needed air circulation.

In spring, when you uncover the mound, you may find some canes have died back from the tips. Simply prune back into healthy wood, making you cut right above a bud or leaf scar. New growth will develop from those points; eventually flower buds will form on the new growth, provided -- in the case of roses -- new growth arose from above the knobby graft union.

Treat Rose of Sharon just as you would a hybrid tea rose.

Tender rhododendrons could be kept over winter by mounding them, but because their flower buds are already present on branch tips in autumn, you'd be removing any potential blossoms when you cut the stems down to cover the plant. There's certainly no point in that! Instead, form a chicken wire cage around the plant and fill it with fallen leaves. As long as winter isn't too severe and the buds are protected, you'll get blooms in spring.

While white snowball hydrangeas are perfectly hardy here, the more exotic-looking blue and pink flowering hydrangeas (called "big-leaf" hydrangeas) are not reliable this far north. Even so, there seems to be a lot of interest in growing them. But they develop flower buds at the tips of last year's stems, even though the buds aren't obvious like those of rhododendrons and azaleas. Based on their growth habit, mounding them just won't work. You need to plant them in a protected place, then cover them right out to the ends of their branches.

Buddleias, called "butterfly bush" or "summer lilacs" are zone 5 plants. As the names imply, they produce elongated, lilac-like clusters of flowers that act as butterfly magnets. Luckily, the flowers develop on new growth each year, so mounding or even heavy mulching can keep the roots and crowns of these shrubs alive so they'll send out new growth in spring. Because they die back nearly to the ground each winter, however, they rarely grow more than three or four feet tall here.

If you'd like to expand your horizons and try growing other flowering shrubs that aren't considered hardy here, look through reputable catalogs for plants that are rated zone 5. Then make certain the plants bloom on new growth rather than exclusively on stems from previous years. Protect them carefully and you may have a garden that's the envy of your neighborhood!

Look for Minnesota Gardening Calendar
Deborah Brown, Extension Horticulturist

New calendar. Photo credit: U of Mn. Extension Service

The new calendar, Minnesota Gardening, 2001, can be found now at garden centers, book stores, and gift shops as well as local county extension offices throughout the state. Look for a garden shot of golden rudbeckia with purple Russian sage behind it, and a small green sprinkling can sticker.

This new calendar features a page devoted to growing ornamental grasses in Minnesota, illustrated with five color photos from Mary Meyer, our ornamental grass guru. And as always, it has a map with average spring frost-free dates along with a USDA plant hardiness zone map. The calendar also has up-to-date information about the various organizations that serve home gardeners in Minnesota.

What distinguishes Minnesota Gardening from other similar calendars is the fact that it's written specifically with our climate and growing conditions in mind. Each month has a list of timely tips and suggestions for garden and landscape activities, followed by titles of several extension publications, most of which may be viewed on-line as well as ordered from the University or your local County Extension Office.

Though it is chock full of good information, the calendar is also very attractive with its colorful photos of flowers, fruit, trees, and tomatoes. Pick one up for yourself and for your gardening friends and neighbors. You may order them directly from the U, toll-free, at 1-800-876-8636 (outside the Metro area) or 612-624-4900 (in the Metro.)

Buckthorn Control

A new Yard & Garden Brief on buckthorn control has just been posted on-line. The URL is: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h464buckthorncontrol.html

Swarms of Winged Ants
Jeffrey Hahn, Assistant Extension Entomologist

Ant queen. Photo credit: Y & G

Ants swarms have been common in and around homes during September. A swarm consists of new queens and males. They fly out of the nest at the same time which can result in hundreds of insects. Their purpose is to mate after which the new queens fly off to start new nests. When ant nests are in or under a home, swarmers can become accidently trapped indoors.

Some people have been concerned that these flying ants are carpenter ants. Although carpenter ants do produce winged ants, they swarm only in the spring. The most commonly seen ant swarmers now are field ants and cornfield ants. They can swarm any time from July until September. Field ants and cornfield ants construct nests in the soil that are either exposed or concealed under objects. This can include under concrete slabs of homes. A nests under a concrete slab can result in swarmers moving up through cracks in the slab into the interior of the home.

Fortunately, these swarmers are harmless to people and property and their swarming is generally short-lived. Just physically remove these nuisances (e.g. by vacuuming) as they are seen. If you can determine where the ants are coming through the concrete, seal any cracks to prevent their entry (this is probably easier said then done).

Treatment of the nest is generally difficult and impractical. To treat it directly, a professional would need to drill the slab and inject an insecticide into the soil. This is likely to be costly as well as a hit and miss method as the applicator has to guess where the nest is located. Baits are also not likely to work. To be effective, workers need to take bait back to the nest; queens and males do not take bait nor return to the nest. If worker ants are not seen, baiting will not be effective.

Check Your Houseplants for Insects
Jeffrey Hahn, Assistant Extension Entomologist

Hoya. Photo credit: Beth Jarvis

With fall settling in, now is a good time to examine your houseplants, both those that were outdoors and those that remained inside, for the presence of insect pests. The sooner an insect infestation is discovered, the easier it will be to control it. Insects that are overlooked may continue to feed and spread to other plants. These insects are small and a hand lens is often helpful in detecting their presence. Also look for evidence of insect feeding, such as discolored leaves, webbing or honeydew (a sticky substance secreted by some insects)

You can generally control light pest infestations with insecticidal soap or by wiping up the pests with alcohol (do not wash hairy plants, such as African violets). Treat heavier infestations of spider mites with bifenthrin. Spray bifenthrin or permethrin for mealybugs, scale insects, thrips, whiteflies, and aphids. Before treating, check the label to be sure the product you intend to use is cleared for the plant you wish to treat. Keep plants with insect problems isolated from uninfested ones until the pests are eliminated.

Cut Back Iris After Frost
Jeffrey Hahn, Assistant Extension Entomologist

Iris. Photo credit: Beth Jarvis

If you have had problems with iris borers this summer, garden sanitation this fall will reduce their numbers next spring. Adults are active in August and September laying eggs on iris foliage. Once we have a hard frost (down to at least 27º for several hours), adults moths are killed and are no longer laying eggs. This is a good time to remove old iris plant material and any other nearby plant debris. Destroy it by burying it or burning it (where allowed). You can also put plant debris into a properly maintained compost pile.

You should take these steps even if you did not see iris borer damage because there may be other nearby irises which could be a source of borers. If you have had a history of iris borer problems, you may need to apply an insecticide next spring when new growth is about four inches high. Dimethoate (Cygon 2E) is currently labeled for iris borer control. A repeat treatment 10 - 14 days later may be needed.

Use Integrated Approach To Control Fleas
Jeffrey Hahn, Assistant Extension Entomologist

Cat fleas feeding. Photo credit: Nancy Hinkle

In the battle against fleas, it is important to use an approach that controls these biting insects on pets as well as in the animal's environment. You can do this by combining nonchemical and chemical means.

It is important to understand flea biology when preparing to tackle their control. Adult fleas feed on blood and spend almost their entire lives on their favorite hosts, cats and dogs. They also can feed on urban wildlife, including racoons, opossums, skunks, and fox. Females lay eggs that are nonsticky and usually fall to the ground. After 2 - 5 days, eggs hatch into small, white worm-like insects.

They feed on flea feces (commonly referred to as flea dirt), which is largely composed of undigested blood. Larvae eventually make cocoons where they remain for weeks or months. Adult fleas emerge when cocoons are properly stimulated by warmth, carbon dioxide (breath),or vibrations.

A good first step in the fight against fleas is identifying where they are most common. This is usually where your pet spends a lot of time, e.g. eating or sleeping. Because flea eggs don't stick to the animal but drop off, you can expect a lot of fleas in those areas. You can test for the presence of fleas by using the white socks test. Walk through your home wearing white socks. The fleas, attracted by the warmth and movement as you walk, will jump to your feet and ankles. It is easy to see their dark bodies against the white background of the socks. If you are still not sure if and where you have fleas, pest control operators have access to a new light trap (Whitmire Micro-Gen's UltraLight flea trap) that is highly effective in attracting fleas.

Once you have located the flea hot spots, it is a good idea to vacuum, concentrating where you know fleas are present. Regular vacuuming can help reduce flea populations. Throw away vacuum cleaner bags (or if practical, freeze for several days) after using. Vacuuming also removes flea feces, an important food source for the larvae. A steam extraction carpet cleaner is effective in killing all stages of fleas. You should also wash any pet bedding in hot water. Wash any human bedding if it becomes infested with fleas.

Despite these nonchemical measures, you will probably need to use an insecticide. It is important to control fleas in your household at the same time you treat your pets. There are several products available to treat homes, such as permethrin. These products are available in ready-to-use aerosol cans. Spray along baseboards, under and around furniture, in areas where pets sleep or play, and other places where fleas occur.

Methoprene is a type of insecticide known as an insect growth regulator (IGR). Insect growth regulators interfere with the fleas' normal development, causing the immature fleas to turn into non-biting, sterile adults. IGRs are very effective against immature fleas and virtually nontoxic to people and animals. However, they do not affect adult fleas and are usually combined in aerosol sprays with another residual insecticide (e.g. permethrin).

You may also want to consider an experienced pest control service to treat your home for fleas. Their knowledge plus a larger assortment of products allows pest control companies to control fleas effectively.

To control fleas on pets, use a dip, spray, shampoo, or dust that contains a labeled insecticide, such as permethrin or carbaryl. Many of these products are available through veterinarians. When using these products, it still important to treat fleas on the premises. However, there are several new products that are only available through veterinarians that are highly effective in controlling fleas on pets so that it is not necessary to also treat inside homes. These products are very low in toxicity towards animals and people.

Program^TM (active ingredient lufenuron ) is a pill which is ingested by either cats or dogs. Although it does not kill adult fleas, it prevents them from reproducing and laying eggs. Advantage^TM (active ingredient imidacloprid) is a liquid spot-on treatment applied to the back of the neck for cats and between the shoulder blades on dogs. Advantage^TM is effective in killing adult fleas. A third product is Frontline^TM (active ingredient fipronil). It is also applied as a spot-on similar to Advantage^TM. Frontline^TM not only is effective in controlling fleas but also in killing ticks and mites as well.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm

Snow Mold on Turf: Prevention is the Key
Jon F. Powell, Turfgrass Pathology

Snow mold. Photo credit: Jon Powell

In the spring, just after the snow has melted, you see gray patches of dead grass in your lawn. These patches are up to one foot in diameter, the grayish grass has a slimy texture, and you may also see numerous small (up to 1/16th inch) black or brown grains among the dead turf. You don't remember there being any patches before winter and would like to know what went wrong over the winter. Your turf is the victim of gray snow mold.

Gray snow molds are caused by several fungi belonging to the genus Typhula that infect turfgrasses (Kentucky bluegrass, perennial ryegrass, fine-leaved fescue, bentgrass, etc...) when there is moisture present and temperatures are just above the freezing point. These diseases are most severe when there is permanent snow cover before the ground has frozen, but can develop on any turf that is covered by snow for over three months. The snow acts as a blanket to moderate temperatures in the thatch and along with the available moisture, provides the ideal environment for these organisms to grow and infect the dormant turf. Favorable conditions also develop during snow melt when there is abundant moisture at the soil interface from the melting snow. Although the pathogen destroys the foliage of the dormant turf, it generally will not kill the entire plant and the turf will eventually recover later in the spring.

Fortunately, over recent years we have had fairly mild winters in the Twin Cities area that has limited the occurrence of gray snow molds. However this disease can be found in areas where the snow lasts for extended periods such as snow piles, compacted snow, or areas that are heavily shaded. Despite our recent fortune, it is still wise to take a few simple preventive steps in the fall of the year to limit the occurrence of gray snow mold over the winter.

Perhaps the most important preventive step in managing gray snow mold is to reduce the likelihood that moisture will accumulate at the turf surface. The most simple step is to remove leaves that are covering the turf. These leaves will trap in moisture and act as a blanket under snow cover providing optimal environmental conditions for the gray snow mold pathogen. Lowering the height that you cut the turf at the time of your final mowing will also help prevent snow molds. Turf that is maintained at a higher cut will trap in more moisture just like the blanket of leaves. By lowering the height, the turf traps less moisture which is less favorable for disease. Since available moisture is so important to the development of gray snow molds, cultural practices to promote drainage, such as core aerification are beneficial in reducing surface moisture and thereby reduce disease.

Snow mold-close up. Photo credit: Jon Powell

The other thing that you need to consider in managing gray snow molds is timing of fertilizer applications. Turf that is lush and growing vigorously going into dormancy is much more susceptible to gray snow molds that is turf that is allowed to adequately harden off into winter. To help this process along it is recommended that late fall fertility be applied after the turf has gone dormant (has stopped growing and no longer needs mowing). This dormant fall fertility is also beneficial to the turf as the nutrition is directed toward the development of the root system of the plants since the roots are still growing in the warmer soil. It is this root system that is vital to the survival of the turf over the coming year.

Although fungicides are effective for managing gray snow molds, by implementing the few cultural practices listed here, the occurrence of gray snow molds can be greatly reduced. If some gray snow mold develops, keep in mind that the turf will most likely recover on its own with a little patience on your part.

Fun Fact: Fall Blooms On Spring Flowering Trees
Beth Jarvis, Yard & Garden Line Project Coordinator

Trees and shrubs that bloom very early in the year set flowers right after they finish blooming. Occasionally, you may see a stray bloom on a lilac or apple tree in the fall. This is not due to any unusual weather, etc. It's simply because the plant senses that daylength, though fall, is the same as spring and that triggers the bloom.

Editorial Notes

Turtlehead and bumblebee. Photo credit: Beth Jarvis

I should have taken one last photo. The slides at left are of a bumble bee crawling into a turtlehead (Chelone sp., pronounced: ke-LO-nay) bloom. The bee really struggled to pry the petals apart and get in. But he did, and finally all I could see of him was one back leg sticking out between the petals. That's the picture I should have taken. In no time, he backed out of the blossom and headed off for another.

In October, four candidates will be intereviewed for the Extension plant pathologist position that came open when Chad Behrendt left the Yard & Garden Clinic. It will be wonderful to have the position filled!

Oct.1 also marks the beginning of our monthly publication schedule. We will publish monthly thru March.

In future issues:
*A shoreline restoration project
*An update on the apple bagging project, a non-chemical apple production method for homeowners.
*Soluble salts in soil tests--what does it mean?
*Growing grapes in Mn.
*Conservation biocontrol--what is it?
*Does treated lumber leach arsenic?

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.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

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.

If you have gardening questions, please call the Yard & Garden Line at (612) 624-4771.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist
or to unsubscribe, enter: unsub yglnewslist

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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