Yard & Garden Line News Volume 8 Number 16                                                               October 1, 2006

Features this issue: Preventing Frost Cankers/Sunscald and Frost Cracks…Wrap or No Wrap? Starting Stem Cuttings to Keep Tender Perennial Favorites through the Winter Fruit Flies In Homes Wet Weather Brings Fuzzy Raspberries Garden Calendar Editorial Notes

Preventing Frost Cankers/Sunscald and Frost Cracks…Wrap or No Wrap?
Gary Johnson, Urban and Community Forestry,
Rebecca Koetter, Research Assistant
Winter temperatures wreak havoc on our Midwestern landscape trees, often causing frost cankers and frost cracks on tree trunks. For many years, trunk protective wraps were touted as being very beneficial in preventing trunk damage from the sun. Unfortunately, research to date has yet to prove conclusively that trunk wraps prevent anything; they may even cause more problems. The conundrum is that some experience suggests that trunk damage from winter temperatures may be prevented by tree wraps applied in the winter.

Fig 1: Frost Canker Photo Credit: Gary Johnson

Sorting Definitions
Frost cankers - a.k.a. sun scald - (Figure 1) may appear as longitudinal splits on the south or southwest sides of the bark along the main stem or branches, or simply as sunken dead areas. Practitioners speculate that cambial tissues are damaged when trees begin coming out of dormancy and are subjected to sudden temperature changes in the late winter/early spring.

Frost cankers are often mistaken for frost cracks. Frost cracks (Figure 2) are formed during extreme winter temperature fluctuations (i.e., when temperatures plummet) and can be found on any side of the stem or branch. These are similar to frost cankers in that they are longitudinal; however, a true frost crack extends into the stem's wood.

Fig 2: Frost Crack. Photo Credit: Gary Johnson

More About Frost Cankers
Some young, thin and/or smooth-barked species like maples, crabapples, and lindens seem to suffer more from frost cankers. Perhaps these young trees are more susceptible since they have yet to develop thick outer-bark tissues. In the Midwest, frost cankers occur primarily during late winter months when the afternoon sun is heating the bark cambial tissue but temperatures are still dropping well below zero at night. Although it is common to claim that a particular tree species is susceptible to frost cankers, transplant stress, and, more importantly water stress caused by root loss during transplanting may be the leading predisposing factor to frost cankers regardless of species.

Tree Wraps: What Do They Actually Do?
Photosynthesis occurs in the stem too! The thin bark of younger trees is composed of photosynthetic organelles that may have the ability to re-fix CO2 during respiration, part of a process called corticular photosynthesis. Throughout the year, light penetrates the organelles and sunlight energy is trapped.

As the tree ages and the bark becomes thicker and woodier, or if stems are wrapped, less light reaches the photosynthetic organelles (University of Illinois, 1997). Stems are part of the photosynthetic cycle, meaning that even during the dormancy of winter the sugars necessary for a young tree's life can be produced.

Are Wraps Harmless?
Trunk wraps or other protective wraps have long been used to protect against winter temperature fluctuations. However, one report found that common paper tree wraps may have the opposite effect; they actually cause a faster rate of temperature change (Litzow and Pellett, 1983). Trunk protection via paper wraps and plastic guards has also been found to retain moisture between the wrap and the tree, which creates an inviting haven for insects, fungi and bacteria. So avoid the problem and remove all stem coverings before spring if you choose to use these products.

Figure 3: Paper wrapping gone bad. Photo Credit: Gary Johnson

Finally, the worst scenario is plain forgetfulness. If a person forgets to unwrap the materials on the growing tree, the wrap remains in a fixed position and may eventually girdle the stem, possibly inuring or killing the tree.

What Does Help?
So, trunk wraps may not reliably reduce winter stem damage from the sun. However, there are some research-based recommendations that should be heeded. 1. Avoid water stress in newly planted trees. Predisposition to frost cankers has been associated with trees stressed by root loss and dry soil conditions. Water the upper 6-8" of the soil- but don't flood it! - throughout the growing season until the soil freezes for 1-3 years after planting a new tree. 2. Don't stress your trees! Plan before you plant. Frost cankers and other preventable problems are often caused by stresses that result from putting sensitive trees in poor locations such as water-logged soils, restricted rooting areas, dry and sandy soils, or areas surrounded by concrete or black top. 3. Do not wound the tree's stem. One of the main causes of frost cracks is a "flush cut" pruning wound, or any accidental wound to a young tree's trunk. For proper pruning techniques visit: http://www.na.fs.fed.us/spfo/pubs/howtos/ht_prune/prun001.htm

For More Information:
Appleton, B.L. 1993. The latest word on tree wraps: less may be better. Arbor Age: vol. 13, no. 12, pp 8, 11-12.
Appleton, B.L. 1994. Use and misuse of tree trunk protective wraps, paints and guards. Technology Bulletin. Forestry Report R8-FR-44.
Harris, Richard W., James Clark and Nelda Mathey, 2004. Arboriculture: Integrated Management of Landscape Trees, Shrubs and Vines, 4th edition. Prentice Hall.
Litzow, M. and H. Pellett. 1983. Materials for potential use in sunscald prevention. Journal of Arboriculture 9(2) pp. 35-38.
Miller, R.W. 2002. Frost cracks and sunscald: bad weather or bad management? Wisconsin Urban and Community Forestry 10(3) pp. 1 and 4.
Roppolo Jr., D.J and R.W. Miller. 2001. Factors predisposing urban trees to sunscald. Journal of Arboriculture 27(5) pp. 246-254.
Rosacker, A. 2005. Stem Morphology for Quaking Aspen (Populus tremuloides) and Limber Pine (Pinus flexilis). Mountain Research Station, University of Colorado- Boulder. http://culter.colorado.edu/~kittel/WEcol_Projects05/WinterStratQuakingAspen&LimberPine.ppt **
Shigo, A.L. 1993. 100 Tree Myths. Sherwin Dodge, Littleton, NH.
University of Illinois. 1997. Plant health care for woody ornamentals. Printec Press, Champaign, IL.

**If you don't have PowerPoint, here's a PowerPoint viewer to download. Takes about 5 minutes at 56 Kbps. http://www.microsoft.com/downloads/details.aspx?FamilyID=428d5727-43ab-4f24-90b7-a94784af71a4&DisplayLang=en

Starting Stem Cuttings to Keep Tender Perennial Favorites through the Winter
David C. Zlesak, Regional Extension Educator, Horticulture

Prepared cuttings of verbena, lantana, petunia, heliotrope, geranium, lavender, rose and rosemary (left to right). All Photos: David Zlesak

Easily-rooted cuttings may be started in water. Transplant when roots are short for best results.

Some plants have root initials or even developing roots before the cutting is even taken such as in the case of Dichondra.

Roots form more readily at nodes in roses as well as many other species.

New shoot growth is a clue that the cutting has rooted.

Two and a half week old coleus cutting rooted in sand is ready to be transplanted into potting mix.

Roots coming out of drainage holes is a sure sign at least some of the cuttings have successfully rooted.

A carefully removed pot reveals a well-developed root system on these rose cuttings which are ready to transplant.

The cool chill of fall is in the air and one morning very soon, if not already, we will wake to see frost blanketing the landscape. Some of our tender plants will succumb to it (i.e. coleus and impatiens), while others can hang on until the temperatures dip into the mid 20's F and we experience a freeze (i.e. geraniums and petunias). We don't need to say farewell to all our favorite tender ornamentals and herbs. Many are truly perennial (short or long-lived) in their native habitat and can continue to grow as long as temperature, light, and moisture levels are suitable. Bringing these beloved plants into our homes for a winter vacation can help to keep our spirits high as we enjoy them and dream about the growing season ahead.

Traditions are plentiful for how gardeners overwinter herbs, geraniums, petunias, and various other "posies". I remember as a young boy helping my grandmother dig and shake off soil from geraniums. We stuffed them into paper bags and nestled them under her bed. Come March, when they were nearly dead, she would cut most of the top growth back, repot them, and put them by the living room window. Surprisingly, they would grow and have some flower buds formed when it came time to bring them outdoors again after the threat of frost. We would dig and pot other plants like petunias before a freeze, cut them back some, and place them on the windowsill where they would branch out and continue flowering throughout the winter. Others prefer to have their potted treasures "hibernate" in a cool and relatively dark basement or root cellar and periodically check them for water. Typically by spring such plants would no longer be hibernating and have long, light green or white shoots reaching for light. Anyone who has tried the hibernation method knows it can be tricky to successfully transition leggy plants back outdoors again. All of these methods rely on preserving the original plant and often results in bringing in insect and disease pests. In addition, the vigor of aged plants can decline as they develop thickened, almost woody, stems.

My favorite method to overwinter tender herbaceous materials is to start softwood stem cuttings (actively growing shoot tips) in late summer or fall before cold temperatures have damaged plant tissue. Vigorous and healthy softwood cuttings can be carefully inspected and washed to remove potential insect pests. In addition, the young, vigorous plants that are produced from such cuttings are relatively small compared to mature plants and can more easily fit into limited and premium windowsill and artificial light space. Multiple new plants can be started from a single stock plant to increase numbers for one's own benefit and to share with gardening friends. One can also successfully root stem cuttings of roses in the fall and enjoy rose flowers throughout the winter. Other woody plants can also be propagated from stem cuttings in the fall as well. By spring it can be surprising how much rooted cuttings have grown (considering how long our Minnesota winters are, maybe it shouldn't be surprising). As plants grow throughout winter one can even take cuttings from the original rooted cutting to continue to increase plant numbers. It can be easy to get carried away. For instance, from one chrysanthemum cutting in September, I generated 300 plants by spring!

Learn if the plant you are interested in propagating has an active plant patent (plant patents are effective for 20 years). Propagation of patented plants is a violation of patent laws unless one has a license agreement with the patent holder.

All three major plant organs typically need to be present to have a viable, sustainable plant: stems, leaves, and roots. When trying to propagate plants through cuttings we can take sections of tissue (often just one or two of these organs) and encourage the missing organ(s) to be regenerated. Some plants are more amenable than others at regenerating missing organs and factors such as time of year and particular species or cultivar can also influence success. Stem cuttings with leaves are often the easiest and most reliable tissue to use. The leaves can continue to photosynthesize and produce energy to help fuel the initiation and development of a new root system typically off of stem tissue.

Taking the cutting:
Exactly how large the cutting is and how many leaves to retain depends on the species and its growth habit and the size of the rooting environment (pots and covers) you choose to use. For most species a 3-4" stem cutting with a few leaves works great. A tip cutting can be used with the growing tip left in tact or sections of stem with the growing tip removed (in the accompanying photo one of each cutting type was made from heliotrope). It is generally recommended to cut ¼" below a leaf at the lower end of the cutting. Remove leaves on the lower portion of the cutting so they are not buried under the rooting medium and rot. Remove flowers as well. The use of a commercial rooting powder or liquid is very helpful to decrease the time to rooting and increase overall percent of rooted cuttings for many species. Coat the basal tip of the cutting with rooting powder (generally ¼ to ½" of the stem is coated) and gently tapping off excess powder. Alternatively, the ¼ to ½ " of the basal tip can be dipped into rooting liquid. To insert the cutting into the rooting medium create a hole in the medium (pencils or fingers work well) and gently position the cutting. Generating a hole in which to insert the cutting helps to keep rooting powder at the base of the cutting and to not to unnecessarily damage or break a cutting by using too much pressure during insertion. Multiple cuttings can be put into a single pot or tray and excess leaf material can be removed or trimmed in order to better fit multiple cuttings. After cuttings are inserted into the medium they should be watered in to settle the medium and have good contact of the moist substrate with the cutting.

Keeping cuttings moist while they root
The most critical factor in rooting softwood cuttings is typically keeping them hydrated until a healthy root system forms. Some plants like coleus and mint are so easy to root that just putting softwood cuttings in a cup of water will supply the necessary moisture and roots will form directly in the water. This especially works well for plants adapted to waterlogged soils and plants having root initials already formed in stem tissue which can quickly expand into elongating roots. Plants with pre-formed root initials include English ivy, Dichondra, and willow. Sometimes root initials can even be seen as bumps at or near nodes, the place where the leaf connects with the stem. Changing the water every few days can help prevent microbial buildup and rot. Many plant species are not amenable to rooting in stagnant water because more oxygen is needed at the base of the cutting than what is typically available. In addition, water-formed roots can be brittle and easily break during the transition to soil and such plants can experience a week or more of transplant shock as the roots adapt from water to a potting mix. Rooting in stagnant water is a very convenient method for those species amenable to it, but with just a little bit more effort healthier plants and rooting of many more species are possible.
A good rooting medium is one that is porous enough to allow air near the base of the cutting, yet also holds moisture. A number of medias are suitable for rooting cuttings and include coarse sand, perlite, and vermiculite. Avoid garden soil which may contain microorganisms which can attack and rot cuttings. One mix that has been especially successful home gardeners is two parts coarse perlite: one part peat moss. In addition to allowing both moisture and oxygen to the base of the cutting, it is important to keep the humidity high around the cutting to reduce the rate of water loss from foliage. Humidity can be elevated by using clear plastic domes or bags supported over cuttings. Allow cuttings to have bright, but indirect light. The full mid-day sun even in winter may cause the temperature within the plastic to rise and damage cuttings. Periodically check to see if additional moisture needs to be added and remove any fallen or diseased foliage.

Acclimating and potting up rooted cuttings
When shoots of cuttings begin to grow it is often a clue that root formation has occurred and cuttings may be ready to be potted. One can check the bottom of the pot to see if roots are visible from drainage holes or the pot can be gently slipped off to observe if roots have formed around the perimeter of the medium. Resist the urge to frequently break apart the medium or pulling on cuttings to see if they have rooted. Newly formed roots can be broken off which can delay root development and provide wounds for pathogens to penetrate the cutting. After cuttings are well-rooted (generally a couple to few inches of roots are adequate), slowly raise the corner of plastic domes or slowly open plastic bags over a period of a week to slowly decrease humidity and acclimate the plants. Depending on the species and environment, cuttings can root in only a couple weeds (such as is typical for coleus) or they can take a month or more to root. Rooted cuttings can be transplanted into your favorite potting medium and grown on and watered and fertilized as other house plants.

More on rooting powders and liquids
Rooting powders and liquids contain the plant hormone auxin. Hormones are chemical substances which at low concentrations profoundly influence growth and organ differentiation. Auxin promotes plant cell elongation and root initiation. Rooting powders contain primarily talcum powder with a small concentration (typically 1,000 parts per million for what is available in garden centers) of primarily the auxin indole butyric acid (IBA). Sometimes the auxin naphthalene acetic acid (NAA) is also included as well as a fungicide. The primary naturally occurring plant auxin is indole acetic acid (IAA), but it is not as stable and does not store as well as IBA or NAA. As a result IAA is not generally commercially available.

Auxin can be produced naturally in multiple places in plants, but generally is produced at the highest concentrations in shoot tips and side buds in leaf axils. Many plants produce more roots at nodes. Higher naturally occurring auxin levels at nodes (site of side or axillary buds) can be attributed to greater rooting in this region and is why it is recommended to cut just below a node when taking a cutting. IBA is naturally found in some plants and at relatively lower concentrations than IAA. NAA is not a native plant auxin. In the 1980's Dr. Jerry Cohen, world-renown auxin expert and professor in the Department of Horticultural Science at the University of Minnesota, and his colleagues identified IBA as a naturally occurring auxin in plants. This had significant implications to the nursery industry by preventing IBA from being pulled from the market for additional testing. At this time there was a general tightening of regulations on synthetic compounds in general by US regulatory agencies. Dr. Cohen's research came out at a time which helped to keep an uninterrupted supply of IBA commercially available and the US horticultural propagation industry strong.

List of potential plants to take cuttings from and grow throughout the winter:
Angelonia Argyranthemum Ageratum Alternanthera Bacopa Begonia Calibrachoa Coleus Fuchsia	Gaura Geranium Helichrysum Heliotrope Impatiens Iresine Lantana Lavender Mints	Ornamental Sweet Potato Osteospermum Pentas Petunia Rose Rosemary Thyme Variegated Glechoma (creeping Charlie) Verbena Vinca vine

Fruit Flies In Homes
Jeffrey Hahn, Assist. Extension Entomologist

Fruit flies. Photo: Jeff Hahn

This is a good time of the year to be aware of fruit fly problems in your home. Fruit flies, Drosophila spp., are about 1/8th inch long, have a tannish body, and a dark-colored abdomen. Probably the easiest method to identify fruit flies is by their bright red eyes. However, their eyes appear darker after they are dead and may not be as distinctive. The larvae are small whitish legless maggots that are carrot shaped and lack a distinct head.

Fruit flies are annoying especially if many of them are present. Although not normally associated with disease, they do have the potential to vector disease organisms if they have visited excrement or uncooked meat.

Don't assume that every small-sized fly you see is a fruit fly. While fruit flies are common in homes, so are moth flies, phorid flies (also called humpbacked flies), and fungus gnats. You can usually distinguish between them as only fruit flies have red eyes. It is important to know which fly is present because how you eliminate them can vary depending on the fly species that is present. If you have any doubts as to what flies are present, let an expert identify them for you.

Fruit flies can be carried into homes in fresh fruits and vegetables or they could fly in from the outside. Once in homes, they are attracted to fermenting and souring smells, e.g. around garbage containers and produce that is starting to become overripe. Fruit flies lay their eggs in a wide variety of sites as long as they are moist, contains fermenting organic matter and are in reasonably undisturbed places.

You can take preventative measures against fruit flies by eating fruits and vegetables while they are fresh or refrigerate them. Do not allow produce to sit out and become overripe. Clean any food residue that accumulates on the inside of garbage containers. Rinse bottles and cans that you recycle. Remove recyclables on regular basis. Periodically clean recycling containers to prevent a build-up of food residue. Remove garbage in tied plastic bags on a regular basis.

If you have a problem with fruit flies, the most effective, permanent control is sanitation, i.e. eliminate their food source. Fruit flies are commonly found infesting overripe fruits and vegetables like bananas, tomatoes, potatoes, and onions. Also look for them around soft drink, wine, and beer bottles and cans that are being saved for recycling as well as in the recycling container itself. Another common site is trash containers especially when it is lined with plastic bags (look between the liner and the container). Remember that the source of the infestation may not be where the adult flies are found.

There are also plenty of unusual sites where you may discover fruit flies. You may need to be a detective and be imaginative to determine where they are coming from. In one case, fruit flies were infesting a tea maker after tea was brewed but was not cleaned out before it was put away. In another instance, they were found in rotting osage oranges (non-edible fruit that are purported to repel insects, spiders, and rodents) that were left out and forgotten. Remember that fruit flies are found in moist, undisturbed places where fermenting organic material is found.

People may be tempted to spray fruit flies with an insecticide. While that will kill the flies you see, it is not a long term solution and more will return. Just spraying adults has no impact on the source of the infestation and the larvae that are developing. As long as a food source still exists, adults will continue to be present.

Fruit fly traps (either store bought or homemade) generally do not eliminate fruit flies. They certainly can capture a number of individuals, but like spraying, it is difficult to control flies by just trapping them. However, traps are useful in narrowing down where the infestation is located. By placing traps in every room, the trap with the most fruit flies usually indicates approximately where the problem can be found.

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

Wet Weather Brings Fuzzy Raspberries
Michelle Grabowski, Regional Extension Educator, Horticulture

Botrytis spores. Photo credit: Beth Jarvis

Infected fruit. Photo credit: Mn Extension Service

Mummy berry. Photo credit: Mn Extension Service

This autumn's cool wet weather combined with a ripening crop of fall raspberries has created the perfect environment for Botrytis cinerea, also known as gray mold. Botrytis cinerea can attack a wide range of plants including fruit, flowers, and weeds. The fungus has the common name gray mold, because it covers infected plant parts with velvety grey spores. Botrytis infects raspberry plants when the canes are flowering. This infection can occasionally cause flowers to turn dark, die and produce gray powdery spores. More commonly, however, the fungus infects the raspberry flowers without obvious symptoms and then goes dormant until fruit begin to mature. When cool wet weather and ripening fruit occur at the same time Botrytis comes out of dormancy and can rapidly spread through a patch of raspberries.

. will turn tan and look watery, with time the infected drupelets will become covered in grey powdery spores. As the infection spreads the entire fruit may become covered in velvety gray spores. Unharvested fruit with Botrytis dry up, become fruit mummies and remain on the cane. The spores from these mummified fruit will spread the infection to other ripening fruit. If infected fruit are harvested, the fungus can spread to healthy fruit in the bowl even when stored in the refrigerator.

Botrytis can also infect mature or dead raspberry leaves. From the leaves the infection moves into the main stem or cane of the plant, resulting in a long brown lesion on the raspberry cane. Small black oblong raised resting structures, called sclerotia, develop within the stem lesions. Sclerotia are important because the fungus can survive the winter in this form. Botrytis can also survive in mummified fruit, dead leaves and weeds. All surviving Botrytis infections produce spores the following spring in wet weather. These spores infect flowers and cause fruit rot the following season.

To reduce disease on this years fruit, harvest healthy berries early in the morning when berries are cool and firm. Take care not to bruise or injure fruit and refrigerate fruit after harvest. Berries are more susceptible to Botrytis fruit rot the riper they get. It is important to pick raspberries just as they ripen. At peak season, this may mean harvesting every day or two. Ripe raspberries should be completely red and pull away from the pedicel (flower stalk, small green leaves and white fruit receptacle) with a slight tug. Diseased fruit should be removed from the patch and thrown away or they will spread Botrytis fruit rot to other fruit. Any berries in the harvest bowl showing signs of Botrytis fruit rot should be sorted out and thrown away. Botrytis fruit rot will spread to healthy fruit even in a refrigerator.

To reduce disease the following year use cultural practices that increase air movement and reduce leaf and flower moisture in the raspberry patch. Second year canes should be cut out of the patch once they are done fruiting. For summer bearing raspberries this is typically done after the final harvest. For fall bearing raspberries, canes are typically cut the following spring. Removing old canes, dead leaves, mummified berries and weed from the patch will greatly reduce the amount of fungi able to survive and cause disease the following year. In addition, thinning the patch and trellising canes will improve air movement in the patch and further reduce disease problems. See the following extension article about how to properly prune and train raspberries. http://www.extension.umn.edu/distribution/horticulture/DG1108.html

Contributors: Nancy Rose Patrick Weicherding Bob Mugaas David Zlesak

Flowers, Fruit and Vegetables:

Geranium maculatum Photo: Beth Jarvis

Dig any tender bulbs that you've not already pulled. See the sheet Storing Tender Bulbs and Bulblike Structures for details.

Tender plants should be inside. Be sure to wash them off outside before bringing them indoors. Be certain to wash the undersides of leaves to dislodge unwanted guests.

Take cuttings of tender plants. (See article on same.)

If you have perennial plants in containers, either plant them in the ground or plant them container and all in the ground, water them in and mulch heavily.

Plant any leftover bulbs now. See: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h120bulbs-spring.html Large-sized (forcing size) bulbs can be potted up and forced in an old refrigerator or a chilly corner of the basement (or a window well w/a cover over the top.) Look for the largest bulbs you can find.Forcing Bulbs for Indoor Beauty in Winter Hyacinths, crocus, daffodils, etc. "forced" in water need four to eight weeks at 50°F and in the dark to develop roots.

Amaryllis can either be grown on as a house plant or let to dry down and go dormant. Check for insects on the leaves.

Spread completely composted compost or nearly completed compost in garden beds to free up space in the composter for fall leaves and garden waste. Pull frost-killed, healthy plants and compost them.

In the garden, rake up any diseased leaves or fallen, diseased or insect-infested fruit and toss it into the garbage. Home composting doesn't get consistently hot enough to kill diseases or most insects that overwinter in fallen fruit or plant debris.

It might not be too late to plant a cover crop. Food for thought can be found at: http://www.extension.umn.edu/horse/components/pdfs/covercrops.pdf
or Green Manure Crops for Minnesota.

Plant garlic within a week or two of the first hard frost. Our reading list includes: http://www.extension.umn.edu/distribution/cropsystems/DC7317.html http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h203garlic.html, and http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Sept0105.html

Harvest fruit that's still there, as it ripens. Clean up windfalls to reduce insect harborage for next year.

Disconnect and drain hoses and drain backflow preventers. Empty and store any pots, such as terra cotta, or bird baths that might break when water freezes in them.

Lawns

The EPA will not be re-registering the post-emergence arsenicals MSMA, DSMA, or CAMA (cacodylic acid) used in summer time crabgrass control. Spring time pre-emergence is still the most effective method of control for crabgrass. Unless other products are packaged for homeowner use, summertime crabgrass control will only be available through lawn care companies. More info to follow.

Now to the middle of October is a great time for broadleaf weed control.

Grass doesn't need as much water now as it did during the summer, however, lawns should get enough water to sustain growth. An inch of water may suffice for up to several weeks. A bit of drough stress will encourage grass to harden off for winter while excess water may prompt succulent new growth.

Mow as the grass needs it. Lawns are still growing in the fall. As days shorten, grasses store food in the roots to fuel overwintering. The end of October is a good time for one final fall fertilizer application (in the TC area). If you want to reduce mowing height, do so over two or three mowings to two inches.

It's ok to mulch-mow leaves into your lawn, just don't leave clumps of chopped leaves on the lawn surface. When you're done, your lawn should look as if it's been raked, with no leaf residue apparent.

To get the leaves chopped finely enough to disappear, you'll probably take a couple of passes at the leaves. Dry leaves are easier to mow than wet leaves and remember to wear a dust mask and goggles as dry leaves are dusty.

It's much too late to over-seed, though you can sod into middle of October. Home lawns could still be core aerated up to mid- to late October. Unfortunately, vertical mowing/power raking is not an option. (It beats up the lawn.)

Trees and Shrubs

It's still ok to plant containerized trees and shrubs but do it as soon as possible.

Mulch all woody plants with approximately 3 inches of mulch. Keep mulch away from tender bark of newly planted tree.

Water until soil freezes up, this is especially critical for newly planted material. Also, now is the time to surround tender parbed trees and shrubs with 1/4" mesh hardware cloth. The hardware cloth is to deter voles and rabbits from girdling the bark or eating branches.

It is safe to prune elms and oaks now, but it's not the best time to prune trees. Wait until late winter/early spring to prune.

Editorial Notes

Different impatiens. Photo: Beth Jarvis

David Hanson will write about winter-injury and any correlation with growing evergreens in too much shade for Nov. 1. I'm planning to visit with the Arboretum plant curator, and some research folks at the Horticulture Research Center and write up those visits. Also upcoming is an article by Nancy Rose on the trees of the family Fabaceae (bean trees).

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/.

Deb Brown will be answering a few gardening questions with Cathy Wurzer on MPR, the first Friday of the month during the fall and winter, between 8:30 and 9:00 a.m. Then in spring, she'll be back at her regular schedule, 10 a.m. the first Friday of each month. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations. (Scroll down for map.)

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

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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