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Thursday, May 26, 2005 05:30 am

gardening 5-26-05

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Master gardeners with the University of Illinois Extension receive hundreds of calls each month from homeowners worried that their prized plants have suddenly taken a turn for the worse. A tree leafed out fine, but then the leaves quickly turned yellow and dropped. Sometimes the problem is easily remedied; sometimes it’s serious. How do you know when the problem is really a problem?

The first step in diagnosing any plant problem is identifying the plant. Different species of plants have different problems.

During cool, wet springs, some trees are prone to anthracnose, a fungal disease. Symptoms of anthracnose include water-soaked spots, brown-to-black spots, brown-to-black blotches, and sometimes death of an entire young leaf. Rarely does anthracnose cause all foliage to die. Because the fungus infects the first set of leaves, a tree such as a sycamore will appear to leaf out late or have sparse leaf cover.

Severe anthracnose can be a problem for sycamore, ash, maple, and oak trees. Sometimes anthracnose appears on birch, sweet gum, and walnut trees. Generally anthracnose is not life-threatening, and the tree will eventually get new leaves. Watering during periods of drought will help the tree produce a new flush of foliage. Once symptoms of anthracnose appear, fungicide sprays are not effective.

To determine whether branches will be able to leaf out again, look for green, plump buds on the twigs. If the buds or branches are dead, the tree may have another, more serious problem.

To learn more about anthracnose diseases of shade trees, visit the University of Illinois VISTA Web site, www.ag.uiuc.edu/%7Evista/horticul.htm.

Keep in mind that not all plant problems are caused by infectious diseases or insects. Many plant problems are environmentally caused.

For example, a few weeks ago, many new leaves were damaged by cold temperatures. Frost damage ranges from brown-to-black leaf tips to the death of all of the leaves on a tree, depending on the severity of the frost. Frost damage occurs suddenly, usually overnight. It often turns leaves black. Leaves will look water-soaked, then shrivel and eventually turn brown or even black.

Here’s a short checklist of questions to use when you begin diagnosing a plant problem: What is the name of the plant? What are the normal characteristics of the plant? When did the symptoms first appear? What has happened around the plant over the past four years? Has fill dirt been added around the plant? Has a new patio, deck or driveway been built in the plant’s root zone? What are the soil conditions? Is the plant in an area where it might be damaged by animals?

The best management option for plants is to promote healthy growth. Water during drought periods, remove dead or dying branches, and fertilize as needed. A 3- to 4-inch layer of mulch is helpful in conserving soil moisture and providing some weed control. Be sure to keep mulch away from the plant’s stem, however.

If you have a plant with a problem and are not sure of the cause, call your local University of Illinois Extension office. A complete list of offices is available at www.extension.uiuc.edu. If you live in Sangamon or Menard county, call 217-782-4617. A plant sample may be brought to the Sangamon-Menard Extension office, located in Building 30 on the Illinois State Fairgrounds.

Nancy Pataky, plant pathologist with the University of Illinois at Urbana-Champaign, contributed to this column.

Berry-pickin’ time

Many strawberry plants, which were in bloom during the first week of May, suffered freeze damage to the blossoms, resulting in partial to complete crop failure for strawberry growers in central Illinois.

For most growers, the harvest begins this weekend. If the weather cooperates, the strawberry season may last two to three weeks.

One popular area you-pick farm is Jefferies Orchard, about five miles north of Springfield (1016 Jefferies Rd.; 217-487-7582, 217-487-7401, or 217-487-7845, www.geocities.com/jefferiesorchard/jefferies.html.

Remember, always call ahead to check produce availability.

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