Yard & Garden Line News
Volume 6 Number 3                                                               March 1, 2004
Features this issue:
 Lawn Cold Winter
Make a Rooting Pot for Houseplant Cuttings
Bat Ticks
Pruning by Study
Gypsy Moth Trapping Detection
Editorial Notes

Lawn Cold Winter
Eric Watkins, Assistant Professor, Horticutural Science

Winter's icy grip. Photo credit:
Beth Jarvis
Most homeowners probably won't think about their lawn until spring arrives and the ice dam hysteria is but a distant memory. Even though it is now hidden by several inches of snow, there will soon be plenty of activity in your lawn. The most important characteristic of a good turfgrass grown in Minnesota is its ability to survive the winter-replanting your lawn every year would be less than ideal. The grasses commonly used for turf in Minnesota (i.e. Kentucky bluegrass, fines fescue, creeping bentgrass) all have good cold-tolerance. The ability of turf to survive the winter is very complex and involves many different factors. During the winter, turfgrasses are in a dormant state with low levels of metabolic activity. Some turfgrass species, under certain conditions, will not survive the winter. There can also be differences between cultivars of the same species for winterhardiness. In certain instances, freezing injury can lead to the death of turfgrass. The likelihood of this happening varies with species; for instance, perennial ryegrass is more susceptible to freezing injury than is Kentucky bluegrass, which is one of the primary reasons very little perennial ryegrass is used as turf in Minnesota. A grass that can survive cold temperatures is able to protect areas that are important for growth, such as the crown, from damage.

Last fall, when temperatures began to approach freezing, the grass plants in your lawn underwent several changes that protected them during the long, cold winter. The most important process that took place was hardening. Hardening allows the plant to become acclimated to the cold temperatures of winter. In order for hardening to take place, a certain low temperature (above freezing) must be reached-this temperature varies with plant species. The plant then begins to undergo physiological changes that help it cope with the cold temperatures of a Minnesota winter. These changes can include an increase in sugar content (which can serve as a type of antifreeze), cell membrane alterations, and changes in gene expression. Additionally, there is a significant decline in moisture content of the crown tissue, which is vital to plant survival (water in plant tissue can freeze and cause damage). Different plant species can achieve different levels of hardening, which is why there are differences in cold-hardiness between grass species.

Evenly redistributing snow cover.
Photo credit:
Beth Jarvis
A good snow cover can be favorable for turfgrass survival in Minnesota. Snow cover insulates plants from the damaging effects of low temperatures-the temperature at the soil surface below significant snow cover can be several degrees higher than air temperature. Snow also allows oxygen to pass through and reach the plants. When a turf area is covered by an ice sheet, the plants can become smothered. The smothering occurs because the ice sheet can trap high levels of carbon dioxide, which can become toxic to the plant. Additionally, oxygen, which is needed for respiration, is unable to reach the grass plant. For this reason, it is important to remove any standing water from your lawn prior to the onset of freezing temperatures. The presence of standing water on your lawn in the early spring, just after snow melt, can also be problematic. Turfgrass crowns can take up the excess water, putting them at risk should another cold snap occur.

Turfgrass plants are now preparing to resume growth once the proper conditions arrive. These conditions include a combination of warmer temperatures and longer days. A plant's ability to come out of dormancy at the proper time is an important component of cold hardiness. As plants are exposed to warmer temperatures in the late winter and early spring, they begin to deharden, and are therefore at greater risk should sub-optimum temperatures return. The amount of dehardening that takes place can vary between plant species.

Hopefully, diseases aren't active in your lawn; however, there are diseases of cool-season turf that may be active prior to spring. The main group of diseases that could be present is the snow molds. Snow molds can be active underneath snow cover; especially when deep snow cover prevents the ground from freezing. The two most common snow molds are pink snow mold and gray snow mold. You may see symptoms of the disease on your lawn after the snow melts-circular straw-colored patches will form on the turf. In most cases, the disease will probably not kill your lawn.

The turfgrass breeding program at the University of Minnesota will aim to develop turfgrass cultivars that are better able to cope with our extreme winters and specific disease problems. When selecting turfgrass species and varieties to use in your lawn, it is important to examine as much data as possible from climates similar to ours. The National Turfgrass Evaluation Program collects data from across North America on several turfgrass species. This data can be found at http://www.ntep.org.

Make a Rooting Pot for Houseplant Cuttings
Deborah Brown, Extension Horticulturist

Partially planted forsythe pot. Photo credit: Dave Hansen
It's becoming quite apparent that our days are growing longer. Not only does that make most Minnesotans feel better, it will have a positive impact on the plants we grow indoors. Thanks to more opportunity for photosynthesis, houseplants will increase their activity, putting out new leaves and growing additional roots.

This renewed growth signals that it's a good time to take "slips" or cuttings from favorite houseplants to share, or simply to start fresh if the originals have become overgrown and unwieldy. It's also time to take cuttings from geraniums and other plants you've overwintered indoors. Just don't plan to root them in water.

Cuttings often rot in water. Roots that do develop are "soft," succulent, and less sturdy. They float, rather than "push" or grow their way down as they would in potting soil. When you lift the rooted cutting out of the water to transfer it to soil, those roots all clump together, making it difficult to spread them out. Often, a cutting that looked perfectly healthy has trouble with this transition from water to soil, and you may lose it.

Start cuttings in a "solid" medium

It's best to start houseplant cuttings in a more "solid" medium that is able to hold a constant supply of moisture. Clean sand, vermiculite, or perlite may be used. My preference is horticultural grade vermiculite, a naturally occurring mineral that has been heat treated to fluff out, a bit like popcorn. Water clings well to its particles' many ridges.

Vermiculite is light weight, clean, and easy to handle, and may be purchased in bags like potting soil at nurseries and garden centers. There has been concern about asbestos contamination in some vermiculite, but the product available now is not thought to pose a health risk as long as you're not constantly breathing the dust on a daily basis.

Ready to plant. Photo credit Dave Hansen
Assembling materials

To make a rooting pot you'll need a clean plastic pot, preferably six inches or so in diameter, with one or more drain holes on the bottom. You'll also need a 2 ˝ inch diameter unglazed terra cotta pot and a cork to plug its drain hole thoroughly. All that's left is a rooting medium – vermiculite, sand, or perlite – and a paper towel.

Use the paper towel (you'll probably need to trim part of it off) to line the bottom of your large plastic pot, covering its drain holes. This is to prevent vermiculite, sand, or perlite from spilling through. Fill the large pot with dry rooting medium, leaving about an inch of room at the top. Be sure none of the paper towel is exposed after filling the pot with rooting medium.

Cork the clay pot tightly. It will function as a reservoir, so water can't be allowed to leak through its drain hole. Push the corked clay pot into the center of the rooting medium, using a twisting motion back and forth. The top of the clay pot's rim should line up level with the vermiculite, sand, or perlite.

Just add water....

Now water the rooting medium. (Work by the sink; water will come through the bottom of the pot initially.) Next, fill the reservoir with water. As the rooting medium dries, moisture will wick through the walls of the clay pot to keep it moist. All you have to do is make sure that reservoir is always full. Your rooting pot will take care of itself, maintaining just the right amount of moisture to encourage rooting, not rotting. Now the fun begins....

Stick cuttings into the medium

All that's left is to take cuttings and root them. Most plants may be rooted from cuttings taken using stem portions that include two or three leaves. Start at the tip of a stem and work your way back. Stem cuttings should be no more than four or five inches long. Remove the lowest leaf before sticking the stem into moist rooting medium.

Roots should form at the node, or part of the stem where the leaf was attached – an area of rapidly dividing cells. You can also stick individual leaves from African violets, peperomias, jade plants, and other succulents directly into the rooting medium, without stems.

Put your rooting pot on a waterproof tray in bright light. And don't forget to keep that reservoir filled.

Is it time yet?

Cuttings from different plants will vary in how long they take to root. With this container, it's not a problem. After a few weeks have passed, tug gently on the cuttings every so often. When you feel resistance, you know that roots have formed. Scoop the cuttings out as they root, using a spoon or your fingers. Shake a little of the vermiculite off, then transplant the cutting into a small pot with fresh potting soil.

Fill the gap in your rooting pot with additional medium and water it. Then you can stick a new cutting, if you wish. After you've used your rooting pot a couple times, wash the pots and reassemble them with fresh rooting medium. The more times you re-use your rooting pot, the more likely you'll run into disease problems.

Here's a "slide set" you can look at for step-by-step illustrations on making a forsthe pot. It's lots of fun, and it really works well. http://www.extension.umn.edu/distribution/horticulture/components/DG4419.pdf

Bat Ticks
Jeff Hahn, Assistant Extension Entomologist

Bat tick.
Photo credit: Jeff Hahn
There are two types of ticks that can be found in Minnesota, hard ticks and soft ticks. Examples of hard ticks include American dog ticks (also known as wood ticks) and blacklegged ticks (formerly known as deer ticks). Soft ticks are less common; an example would be bat ticks.

While both kinds of ticks feed on the blood of animals (mammals, birds, reptiles), there are differences between them. You can recognize soft ticks from hard ticks as soft ticks have a softer, more pliable integument (their ‘skin') that appears granulated or warty while hard ticks are more smooth. Hard ticks possess a scutum, a hard plate on the upper surface of the tick body behind the head which soft ticks lack. When looking at the ticks from above, you can see the mouthparts on hard ticks but soft ticks' mouthparts are underneath and pointed ventrally (down).

The most commonly encountered soft tick in Minnesota is the bat tick, Ornithodoros kelleyi. When full grown, it is about 1/4 inch long and grayish brown. As its name suggests, it feeds exclusively on the blood of bats. Unlike hard ticks which just feed two to three times and become very engorged with each feeding, bat ticks take smaller more frequent meals. Bat ticks normally stay very close to theirs hosts and their roosting areas and people may not notice these ticks in their homes.

However, if the bats abandon their roost, are forced to leave, or in some way their populations decline, bat ticks will begin to search for new hosts. This can lead them into the areas occupied by people in homes and other buildings. They can bite humans although this does not seem to be common. Their bites appear to cause little irritation and could easily go unnoticed. Bat ticks can not reproduce on human blood and they are not known to transmit disease.

To control bat ticks, it is first necessary to eliminate the bats from the buildings. As long as they remain, they are a reservoir for additional bat ticks. The best method for permanently ridding a building of bats is to exclude them. This requires that all of their entrances are identified and then sealed after all of the bats have left. The best time to do this is late summer and fall. There are not any pesticides to repel or control bats.

It may also be necessary to treat for the bat ticks inside buildings. Concentrate sprays where the bats were roosting as well as in cracks and crevices in other sites where the ticks are hiding. Use a residual insecticide labeled for indoor use, such as permethrin.

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


Pruning by Study
Janna Beckerman, Extension Plant Pathologist

Sir Francis Bacon said: "Natural abilities are like natural plants; they need pruning by study." Late winter is one of the best times to study your trees with respect to pruning, and to examine trees for any structural defects. Without the cover of leaves, deciduous trees are easily evaluated for the presence of cracks, weak branch points, cankers or decay.

The fungus that causes thyronectria canker of honey- locust infects through open wounds. Photo credit:
Bob Blanchette
Proper pruning done at the appropriate time is one of the most important, and unfortunately most overlooked aspects of tree care. The role of pruning encompasses many facets. Pruning is performed as a fundamental part of plant maintenance: Pruning young trees can allow you to avoid future problems when the tree is older, larger and more expensive to fix. Pruning can also be viewed as preventative medicine, by removing damaged or diseased branches you prevent infections from developing and spreading. Finally, pruning serves an essential role in landscaping by encouraging healthy, beautiful growth.

Like most practices, pruning can be done well, and pruning can be done poorly. Proper pruning of trees does not promote future defects. However, improper pruning may solve an immediate problem but result in long-term decay, breakage and even tree death. Before you "embark" on pruning, you need to know what to look for.

Before You Begin
Looking to evaluate your trees for problems is as easy as A, B, C, D and E.
Avoid Disaster!
Evaluate your trees. Doing so can allow you to avoid catastrophe. The risk of oak wilt or Dutch elm disease is negligible most years before April first. The fungi that cause these diseases are not actively sporulating, and the beetle is not feeding. Wounds which would normally attract beetles are compartmentalized before the beetles that vector disease become active, thereby preventing infection from occurring.

Late winter is a good time to prune trees that are susceptible to fire blight, such as apples, hawthorns, mountain-ash and pears. Over three hundred species of insect have been found to vector the bacterium that causes fire blight. Pruning now permits prevents infection from occurring. With fire blight, it is important sterilize pruning tools between cuts. Remember: Never combine pruning for shape with pruning to remove diseased portions of a tree!

Split branches on a dwarf apple due to incipient rot. Photo credit: Plant Disease Clinic.
Branch Unions
Branch unions are simply where a secondary shoot or stem develops off the main stem of the tree. Weak branch unions are places where branches are not strongly attached to the tree. A weak union can occur due to a variety of reasons, but the outcome is always the same: The bark that has developed does not have the structural strength of wood. Under proper branch development, a "branch bark ridge" forms at the upper surface where the branch meets the supporting stem. The "branch bark ridge" is the line of bark that has been pushed up as the branch and supporting stem have grown. Not having a branch bark ridge, or having too much bark structurally weaken the juncture making it prone to breakage. Trees with a tendency to form upright branches (e.g., elm, maple and mountain-ash) are predisposed to forming weak branch unions.

Cankers and Cracks
Cankers are lesions in the stem or branch of a tree. Cankers can be caused by wounding or disease, and often appear sunken. Wounds and injury provide an entry point for many pathogens, like Nectria, Phomopsis or Eutypella to infect and invade the plant. Because cankers structurally weaken the tree, stem breakage commonly occurs at or near the site of the canker. Whenever possible, small cankers should be pruned out. Large cankers, particularly in the main stem of the tree, need to be watched carefully.

Cankers also serve as a site where larger cracks can develop. A crack is a deep split through the bark, extending into the wood of the tree. Cracks often develop when a main stem branches into two large branches, a frequent occurrence in dwarf trees (Fig. 2). Cracks in the main stem are often indicative of tree failure. In the case of large cankers or cracks, consult a professional arborist.

Phellinus tremulae, a heartrot of aspen, forms conks on the outside of infected trees. Photo credit:
Bob Blanchette
Decay and Dead Wood
All living things must die. Most trees or even just branches of trees, in the process of dying, begin to decay or rot. This is a natural process that involves the interaction of the wood, bacteria and fungi. Although to most people any decay is immediately associated with death, the presence of decay does not necessarily indicate that the tree is dying. It may indicate that only a portion of the tree (such as a branch), is dying. Remember, trees do not heal wounds, injuries or diseased portions-they compartmentalize it to keep the damage from spreading. Although this process protects the tree from further damage, it does impact its overall structural integrity of the affected branch or stem.

Decay can be identified by the presence of conks (shelf-fungi) or mushrooms , or by soft, punky wood. Because trees often decay from the inside out due to heart rot, hollow cavities form surrounded by wood that appears solid and sound. Recent straight-line winds in the twin cities metro found numerous instances of tree failure due to seemingly healthy trees that were hollow inside.

Dead wood is readily identifiable due its dry and brittle nature. Dead branches should be pruned out whenever possible. Any decay associated with cracks, weak branch unions, or other defects needs to be pruned out to prevent further injury or cracking to the tree.

Exceptions!
To every rule, there are exceptions, and pruning is no different. Because most spring-flowering shrubs produce flower buds on the previous year's wood, the best time to prune is immediately after they are done flowering each year, and before they set flower buds for the next year. Avoid late winter pruning on those shrubs that flower on old wood. These include bittersweet, deutzia¹, forsythia, lilac, mock-orange and Van Houtei spirea. For additional information, see Maintenance of Deciduous Shrubs at the SULIS SITE. http://www.sustland.umn.edu/maint/index.html

Corrective Actions
Evaluating the problem is only the beginning. Correcting the problems in a proper fashion, and recognizing when professional help is required are next. How to Prune Trees (Bedker, O'Brien & Mielke, 1995) at http://www.na.fs.fed.us/spfo/pubs/howtos/ht_prune/prun001.htm is an outstanding resource and introduction to the study of pruning.

¹ Deutzia is marginally hardy in USDA Zone 4B

Please check out the new diagnostics web pages at
http://www.extension.umn.edu/projects/yardandgarden/diagnostics/


Employment Opportunities at the Minnesota Department of Agriculture
Gypsy Moth Trapping Detection

Gypsy moth
Photo credit: James B. Hanson,
USDA Forest Service
Deadline for Applications: March 12, 2004

Description: The European gypsy moth causes extensive damage when the caterpillars defoliate North American forests. Duties include assembling, setting, monitoring and removing up to 650 cardboard detection traps within a designated route. Requires driving up to 250 miles per day, working in all weather conditions. Trappers collect data using a hand-held global positioning system (GPS) unit (training provided) and report to a lead trapper. Trappers work from home and must live in the area in which they trap. A reliable vehicle is necessary for driving trap routes in case a state vehicle is not available for use. Mileage is reimbursed at $0.375 per mile.

Salary range: $11.16 - $14.58 hourly

Commitment: Mandatory training in Saint Paul, MN on June 3 and 4. Position runs through September 3 (trappers in the north begin trapping later and work until the end of September). Hours: 8:00 a.m. - 4:30 p.m. Monday - Friday. There are two weeks of scheduled unpaid leave during the season, a week off in July and a week off in August, for approximately 11 weeks of employment.

Qualifications: Minimum qualifications are a high school diploma or GED and a valid driver's license. The ideal candidate has a background in biology or a related field, and has the ability to work well with a minimum of supervision and with others as a team. Must be able to set goals and meet deadlines, be flexible and possess good interpersonal skills. Map-reading and navigation skills and attention to detail are critical to the performance of the job.

To apply: Apply on-line at https://statejobs.doer.state.mn.us/ResumeBuilder

You may copy and paste your existing resume or let the software create a resume for you. If you do not have access to the internet and can't submit your resume on-line, submit your paper resume and application to the Department of Agriculture, Attention: Sherry Thomas-Berry, 90 West Plato Boulevard, Saint Paul, MN 55107 or by fax to (651) 297-7868. To be considered for this vacancy, please indicate the job title and/or posting number in the Specific Opening area of the employment application. You must indicate a high school diploma or GED and valid driver's license in your resume to be considered. To receive the paper application to submit, please call Kim Grubbs at (651) 296-2323.

Sherry Thomas-Berry, (651) 297-9514 or Sherry.Thomas@state.mn.us

Editorial Notes

Variegated skunk cabbage. Photo credit:
Beth Jarvis
The photo is from Hortus Botanicus in Amsterdam. The solid green Symplocarpus foetidus is native to Mn. and among the earliest of flowers. I was too late to see the flower as the leaves appear afterward. The leaves stink when crushed, hence the name.

Many of us are anxious for spring. To reflect the returning interest in things horticultural, in April we will return to publishing around the first and the 15th of the month.

Krishona Martinson and Bob Mugaas, Regional Extension Educators, will collaborate on a piece for April 1 on some alternatives of traditional chemical herbicides for weed control. This article came from a request, so don't be shy about sending me your story ideas!

A bit later, we'll hear from Nancy Rose, a regional extension educator, about buying trees and shrubs.

Once upon a time, holes in trees were treated by filling them with concrete. Technology has changed as we've learned that such rigid filling is damaging to the tree. So what's a tree owner to do with that big hole in a tree? Later this spring, Patrick Weicherding will discuss what, if anything, needs to be done with such tree wounds.

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 the components of the Yard & Garden Line, such as Bell Museum of Natural History, INFO U and the Soil Testing Lab. There are new links to the Insect Journal, Plant Disease Diagnostics, Disease Watch and now the Urban Forestry Resources clinic.

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

The Yard & Garden Clinic closed December 12, 2003 due to budget cuts. Questions from the general public will no longer be accepted. Samples will not be accepted.

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


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