Yard & Garden Line News Volume 3 Number 9                                                               June 15, 2001

Features this issue: Putting Houseplants Outdoors for Summer Geraniums A New Way to Keep the Doctor Away! Oak Wilt Is On the Move Red Turnip Beetles In Gardens Has Something Been Eating My Oaks and Hackberrys?? Something Really Is Eating My Trees American Dog Ticks (Wood Ticks) Common This Year Editorial Notes

Putting Houseplants Outdoors for Summer
Deborah Brown, Extension Horticulturist

Houseplants summering outside. Photo credit: Deb Brown

After spending this terrible winter and much of this weird spring cooped up indoors, we all know what it's like to enjoy the fresh air outdoors. If your houseplants had feelings and could communicate them to you, they'd probably plead for an outdoor summer vacation, too.

Why not try it? Warm humid air, soft rains and gentle breezes, and plenty of reflected light combine to create growing conditions far superior to any you can provide indoors. If all goes well, your plants will develop vigorous new growth, and look livelier and more robust by the end of the season.

To accomplish this you should:

* Know which plants can benefit from being outdoors.
* Choose an appropriate location for them.
* Alter your routine care to reflect outdoor conditions.
* Bring houseplants back indoors before it's too cool.

Not all plants do well outdoors. In hot windy weather some plants growing in small pots can dry faster than you may be willing or able to water them. Baby's tears and others that wilt rapidly are particularly vulnerable.

Houseplants with velvety or "hairy" leaves such as African violets or purple passion may fall prey to foliar problems as a result of water that's trapped on their leaves.

You may prefer not to put out plants with large leaves such as selloum philodendrons, fiddle leaf philodendrons, rubber trees, or dieffenbachias. They're vulnerable to damage from heavy rainfall or hail, which may tear their foliage. If you do put them outdoors, set them back along the inner wall of a porch or balcony with a ceiling overhead for protection.

Plants with smaller leaves usually do fine in more exposed locations. But you still must protect them from direct sun, mid-morning to mid-afternoon. Their leaves aren't used to such high light levels and will sunburn easily. Unlike human skin, once plant tissue burns, it can't regenerate.

Earlier and later in the day when the sun sits lower in the sky, direct sunlight won't harm them. The dappled shade found beneath branches of a large tree is just about perfect; the north side of a house or garage would work, too.

You could acclimate your plants to higher light by moving them gradually into brighter locations. But several weeks before bringing them back indoors, you'd have to reverse the process to compensate for winter's shorter days and lower light levels. It's probably better to leave them in dappled light all summer. It's certainly easier!

If you put your houseplants outdoors, check them frequently to see if they need water. Wind and heat dry them more rapidly than indoor conditions. Plants in terra cotta clay pots dry fastest because moisture evaporates right through the container walls.

Outdoor houseplants. Photo credit: Deb Brown

When plants grow rapidly they require additional fertilizer. Continue to mix houseplant fertilizer 1/2 strength, but apply it every two or three weeks while your plants are outdoors.

Plan to transplant the most vigorously growing plants into larger containers several weeks before you're ready to bring them indoors. That way they won't have to undergo two stressful transitions at once.

Don't wait till frost threatens to bring your houseplants in. As soon as night temperatures drop regularly into the mid 50's inspect them for insects, wash them carefully, and put them in your brightest indoor spot for two or three weeks before moving them back to their original locations.

There's no need to spray your houseplants with insecticide unless you find harmful insects present after you've washed them. But do keep an eye on them, just in case.

Geraniums
Deborah Brown, Extension Horticulturist

Hanging basket. Photo: Deb Brown

If our late, cool, wet spring means you're getting a slow start planting flowers this year, take heart. You can still find gorgeous geraniums in a wide array of forms and colors at garden centers and farmers' markets across Minnesota. And they're amazingly easy to grow!

Few flowers rival the visual impact of vigorously blooming geraniums. Their brightly colored clusters of blossoms are both eye-catching and long-lasting. How many other annuals will bloom non-stop from late May or June till they're cut down by frost ..... or you bring them indoors for winter?

Though most commonly grown in window boxes, hanging baskets, and large containers on decks and patios, geraniums can be planted directly into a sunny garden to create a splash of color. They're also effective used as edging plants to unify other colors and elements in the garden. One critical requirement is plenty of light. Geraniums need at least five or six hours of direct sunlight, preferably in the afternoon, to bloom well. You'll get some flowering with only three or four hours of sunlight, but it will be sparse by comparison.

Whether growing in a container or planted directly in the garden, geranium roots tend to rot when moisture collects and soil stays soggy for days on end. You can compensate for this trait (common to many flowering annuals and perennials) by choosing both soil and containers carefully.

Planters in Bern. Photo: Deb Brown

Use only fresh soil marked "sterilized" for potted plants. If it doesn't drain readily, mix it with additional perlite, vermiculite, or clean sand at the rate of two or three parts potting soil to one part soil amendment. Never put garden soil in a container; you may introduce disease organisms, weed seeds, or insects and eggs.....and it often packs together.

Containers must have drain holes unless they're located where rainfall never reaches them. Even then, it's easier to grow geraniums successfully if there are drain holes to allow for the free flow of excess moisture. Remove any attached trays that trap water and allow it to wick back up into the containers.

In the garden, avoid planting geraniums in low lying areas where moisture collects and soil is slow to dry after a rain. If necessary, work in lots of peat moss, compost, or other organic matter to raise the soil level and improve drainage.

Side by side trials. Photo: Deb Brown

Geraniums are relatively modest in their need for fertilizer. Overdoing it can result in lush leafy growth, but fewer flower clusters. Feed geraniums growing in containers with a mild liquid fertilizer meant specially for flowering plants, every three weeks.

Prepare garden soil for geraniums and other bedding plants by turning in two pounds of 10-10-10 per 100 square feet, prior to planting. Then work about half that amount into the soil as side dressing around the plants about mid-July. You could also switch to liquid fertilizer at that point, if mulch makes it difficult to hoe in a granular fertilizer. It's more convenient, but also slightly more costly.

Be sure to "deadhead" or clip off stems of faded flowers. Not only are they unattractive, but some will develop seeds which tends to slow blooming. Remove any yellowing or dry leaves, as well. These leaves, along with faded flowers, can become infected with fungal organisms, particularly in rainy, damp weather.

Geraniums may be brought indoors in autumn to be over-wintered in a sunny window or forced into "dormancy" in the basement. However, the longer you keep them over from year to year, the more likelihood of disease problems. And often, especially if they're not kept growing actively, they'll be very slow to resume blooming the following summer.

A New Way to Keep the Doctor Away!
Vince Fritz, Extension Vegetable Specialist, Southern Research and Outreach Center

A cabbage a day? Photo credit: U of M Ext. Svc.

The old saying, "an apple a day, keeps the doctor away" is on the verge of changing to "eat your cole slaw today and keep the doctor away". The recent flurry of information that has swept across this country on the healthful benefits from eating fruits and vegetables has gone beyond our traditional understanding of the vitamins and minerals they provide. Many of the fruits and vegetables that mom told us to eat because they were good for you, have now taken on a new level of "functionality".

The new term, "functional food", refers to a food item that contains a dietary ingredient that may have health attributes beyond normal nutritional value. Many fruits and vegetables have been identified as having naturally occurring compounds that prevent oxidative damage to our cells which can lead to a precancerous or cancerous condition. These compounds are commonly referred to as "nutraceuticals" or "phytonutrients".

The evolution of vegetable production methods and development of new varieties focussed on improved efficiency and aesthetics, better taste, or disease resistance. Any changes that may have occurred in nutraceutical concentrations as a result, happened by coincidence. Increased consumer awareness regarding additional health benefits from eating vegetables may lead to a new market demand. Many of the vegetable crops in the Cruciferae family that includes crops like broccoli, cabbage, Chinese cabbage, cauliflower, and Brussels sprouts are believed to offer the consumer, this kind of chemoprevention.

A new research program initiated at the University of Minnesota has centered on the development of a method to consistently produce vegetable crops with significant cancer chemopreventive properties. This project brings together horticulturists, plant physiologists, food scientists, and biomedical scientists at the University of Minnesota, along with local and national producer and consumer groups to develop and introduce a new type of vegetable crop to the market. Widespread adoption by producers and consumers may ultimately lead to improved human health and greater profitability.

Check out our web site at http://sroc.coafes.umn.edu, for further updates and other research projects currently conducted in horticulture.

Oak Wilt Is On the Move
Janna Beckerman, Extension Plant Pathologist

White oak with oak wilt. Photo credit: Plant Disease Clinic

After a delayed start this year, oak wilt is up and running rampant in the Twin Cities. On a leisurely, neighborhood disease walk, I came upon a homeowners worst nightmare, and a plant pathologist's dream. In a single yard I saw one already dead northern red oak (Quercus rubra), a dying red oak, and a pin oak (Q. ellipsoidalis) with a flagged branch. This homeowner, and his/her neighbor, were about to lose three trees in a span of a month. As I surveyed the yard, I saw at least three more pin oaks, and…the potential culprit! Approximately 50 ft. away from the dying stand of trees was a white oak (Q. alba) with numerous dead branches.

Oak wilt is caused by the fungus Ceratocystis fagacearum. It can be spread two ways: via root grafts between oak trees or vectored by sap (Nitidulidae) beetles. Root grafts occur when roots of a related species (or even genus, although transmission occurs less frequently) grow together. Trees can form root grafts with other trees as far as fifty feet apart! In the case of oak wilt, the fungus moves through the roots of the dying tree into neighboring oak trees.

Less frequently, oak wilt is vectored by sap beetles. Sap beetles are attracted to two things: 1) the sporulating (spore-producing)mats produced by the fungus, and 2) the wounded oak tree. The fruity-smelling mats of fungus are usually produced between April and late June on red oaks that wilted during the previous summer and weren't removed. Unfortunately, this is also the same period of time that red oaks produce the springwood that is particularly susceptible to infection. If a tree is wounded and visited by a beetle that has recently visited a spore mat, infection by the oak wilt fungus is likely. Red oaks can die as quickly as two weeks after inoculation by the beetle. White oaks can live for years with oak wilt, slowly losing limbs over time.

So, what happened with this stand of oaks? Did the dying white oak in the corner of the yard form a root graft with the red oak? Did the homeowner accidentally back into the first red oak (which was positioned closely to the driveway), wounding it and allowing entry of a sap beetle? There is little doubt in my mind that the second red oak died due to infection by root grafts to the first dying oak. How long before the flagged pin oak dies as well? It's classified as a "red oak" because of its pointy leaves, so will it also succumb as quickly as two to six weeks after infection?

What is left for this homeowner to do? First step is to stop the spread of the fungus through root grafts. This is usually accomplished by severing the roots with a vibratory plow. Because this is an urban situation, they'll need to be certain there are no buried utilities nearby.* If buried utilities are present, the soil sterilant Vapam, can be used to chemically sever the graft. However, chemical means are not as effective as severing the roots. Highly valued but infected white oaks can be treated with the fungicide Alamo® (propiconazole) by a trained arborist. The injection method is similar to treatment of American elms with Dutch elm disease. Treatment with Alamo® has the added advantage of preventing further disease development for two years in the treated tree.

Effective management for oak wilt requires multiple approaches, namely prevention in the form of not pruning or wounding oaks April through June. Even if these approaches are undertaken, oak wilt can still occur, and with devastating results. When it does occur is when a management plan must be undertaken. Very few neighborhoods or even communities have these management plans in place. If you live in a neighborhood with many oaks, do you know what can and should be done if you were this homeowner? Think about it, before oak wilt comes to a neighborhood near you.

*Two working days before you dig, call Gopher One Call at 651-4 54-0002 or 800-252-1166.

Test your diagnostic savvy monthly with Disease Watch at: http://www.extension.umn.edu/projects/yardandgarden/PlantPathWeb/Plpa.htm
Red Turnip Beetles In Gardens
Jeff Hahn, Assistant Extension Entomologist

Red turnip beetle. Photo credit: Entomology Dept.

Red turnip beetles are brick red with 3 black stripes down their wing covers. They have been common this year in central Minnesota where they have been active since the third week of May. These leaf beetles commonly feed on all types of crucifers, including raddish, cabbage, kolorabi, turnips, hoary alyssum, sweet alyssum, wild mustard. They have also been reported by homeowners feeding on strawberries, dandelions and wildflowers. Farmers may also encounter them on the above vegetables as well as rapeseed, and canola.

Feeding can be slight or severe, depending the numbers that are present. Small numbers can be ignored. Try to handpick problem red turnip beetles and put into a pail of soapy water when possible. When this isn't practical, use a residual insecticide, such as permethrin, carbaryl, or diazinon. Be sure the product you intend to use is cleared for the plants you want to treat. Red turnip beetles should not be a problem after June.

Has Something Been Eating My Oaks and Hackberrys??
Jeff Hahn, Assistant Extension Entomologist

Oak tatters. Photo credit: Murrary Co. Extension.

Residents in southern Minnesota, especially in the southwestern counties have been finding many of their oaks (particularly bur and white) and hackberrys looking lacey or skeletonized. People have been noticing this damage since mid May when the trees first began to leaf out. The first reaction is that insects, like cankerworms, are responsible for damaging the leaves. However, when examined closely, these trees have not shown any evidence of chewing insects on them.

Despite the circumstantial evidence, the problem is not defoliating insects but a condition known as oak tatters. The leaf tissue between the veins is damaged either while still in the leaf bud or shortly as the leaf starts to expand. The exact cause of this problem is unknown. It has been speculated to be related to chilling temperatures before or during leaf expansion, or insects feeding or ovipositing on the buds, or herbicides affecting the physiology of the tree, or a combination of these factors.

Fortunately, any new growth that comes out later in the season looks normal. Although it takes energy to put out extra leaves, a healthy tree can tolerate this. If a tree continues to be affected by tatters or other stress it can lose vigor and be injured. It is not possible to predict if trees will suffer from oak tatters next year. Ed Hayes, plant health specialist with the DNR has been observing tatters over the last several years. He finds that some trees suffer from oak tatters in consecutive years, while other trees may be affected one season but not in other years.

There is no control for oak tatters. In a home landscape, you can try to protect your trees from the effect of tatters by keeping them healthy and vigorous through proper watering, fertilizing, mulching. You should also prevent unnecessary stress by not making any changes to the grade or compacting the soil around the tree and avoiding injury to the trunk and roots.

For more information, go to the following link to see the U.S. Forestry fact sheet on oak tatters: http://www.na.fs.fed.us/spfo/pubs/pest_al/oaktatters/oaktatters.htm

Something Really Is Eating My Trees
Jeff Hahn, Assistant Extension Entomologist

June beetle. Photo credit: Entomology Dept.

Have you seen defoliation on deciduous trees in your yard but been puzzled because you have not been able to see any insects? Check your tree when it is dark because the likely culprits are night-time feeding June beetles. They have been especially common on oak but may be also found on other hardwood trees, such as ash and willow. They have been feeding since late May and early June.

Fortunately, vigorously growing, well-established trees can tolerate this feeding and the presence of June beetles should be tolerated when possible. June beetles are not a persistent defoliating tree pest and would not be expected to return to the same trees to feed next year. It is possible that a young or unhealthy tree could be injured from severe defoliation. If you need to protect more susceptible trees, treat them with a residual insecticide, such as acephate, carbaryl, diazinon, or permethrin. June beetles are only expected to feed through June. After that, they lay eggs then die.

American Dog Ticks (Wood Ticks) Common This Year
Jeff Hahn, Assistant Extension Entomologist

American dog ticks. Left female, right: male. Photo credit: Dept. of Entomology

The American dog tick, also known as the wood tick has been particularly common this year. This tick seems to be more abundant during cool, damp springs, like we have experienced this year. American dog ticks are commonly found in open fields and amongst hardwood trees where they feed on a wide variety of mammals, including white-footed mice, voles, chipmunks, raccoons, squirrels, dogs, cats, and people. Although they bite people, they are not a problem transmitting disease to us in Minnesota.

You can usually recognize an adult female American dog tick by its reddish brown body with white markings. Unfed adults are about 1/8 inch long. But be careful as you can't always identify a tick by color and size. There are different species of ticks which can make diagnosis difficult. The same species of tick can look different depending on whether it is an adult female or male, immature, or engorged. If there is any doubt about the identification of a tick, submit the specimen to an expert. This is important as the blacklegged tick, a potential vector of Lyme disease, is also common in Minnesota.

American dog ticks usually take two years to complete their life cycle. During the summer of the first year, the eggs hatch into larvae. These larvae do not feed until the following spring. After one blood meal, they turn into nymphs. After feeding a second time, these immature ticks develop into adults during late summer of the second year. The adults do not feed until the following spring, when the weather turns warm. Adults are common April through June but die after laying eggs, completing their life cycle.

If you are having a problem with American dog ticks on your property, the best tactic is to keep grass and weedy areas cut. These ticks prefer to be in taller grass and are generally not in maintained lawns. When they are found in yards, it is usually near a margin of taller plants. An insecticide application of carbaryl (Sevin) along the border of the lawn and weedy areas can be effective but is temporary. Insecticides should not be applied more than once.

If you plan to walk in an area where ticks are known to be, protect yourself against ticks be wearing long pants and long-sleeved shirts. Wear light-colored clothes so ticks are easier to spot. You can tuck your pants into socks to provide extra protection. Stay in the middle of trails and avoid nearby grassy areas. You can also apply a repellent, such as DEET or Permanone (permethrin). Do not overapply repellents. Check your yourself, other people and pets carefully after returning from areas where ticks are found.

If a tick is found biting (i.e embedded into the skin), carefully remove it with tweezers by grasping it around the head as close to the skin as possible and gently yet firmly pulling it out. Covering the tick with Vaseline or touching it with a hot match does not cause ticks to stop biting. Remember to get a tick identified if you are not sure what it is.

Adult American dog ticks are not active past June. During the month, females lay eggs and then die. Although immature ticks are active later in the summer, they are rarely encountered by people.

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

Editorial Notes

Digital Daisy Artwork: Otso Kallinen By Design

On May 3rd, we launched a Q & A bulletin board service, staffed by Master Gardeners. It is limited to Minnesota gardeners because the Minnesota-hardy plants and gardening practices are the focus of the Master Gardener training. Everyone is welcome to read the board, however, regardless of where you live. The address is:
http://www.extension.umn.edu/projects/yardandgarden/askmg.html

Deb Brown will be on MPR as Katherine Lanpher's guest at 10 a.m. on the first Thursday of the month. (Scroll down to the little radio below for radio info.)

For those of you looking for the treated wood alternatives article, well, so am I. I'll run it as soon as I get it.

July 1, we'll take a timely look at the Minnesota blueberry breeding project. In the July 15th issue, we'll hear from our resident turf disease guru on that orange stuff that gets all over your shoes.

I've also been promised something on tetanus from the Mn. Health Dept. I've been cautioned that tetanus booster vaccine is in short supply. The purpose of the piece is awareness-raising. Several years ago a local gardener died from it. A friend's mom got tetanus a couple of years ago, was quite sick and her recovery took all summer. Who would have thought?

Mary Meyer will write about ornamental grasses in Aug. Bob Mugaas, Hennepin Co., has agreed to comment on fertilizers, whether organic or synthetic is truly superior plus other thoughts he may have on the subject.

This fall, Patrick Weicherding, Anoka Co., will share the latest research on winter injury/frost crack on trees. It may be more stress-related that we've ever dreamed. Sometime next winter, Doug Foulk, Ramsey-Washington, will talk about pears, what to know and how to grow. I'm also lining up articles on other plant breeding projects and will give you an inside look as they are available.

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 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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