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Wet spring could spread disease in many native sycamore trees

THE BALTIMORE SUN

We recently purchased a home that has two large sycamore trees in the back yard. the trees leafed out beautifully this spring, but now they are losing many of their leaves. do you know what would cause this?

The sycamore tree (Platanus occidentalis) is a large and beautiful native tree that is unfortunately subject to several disease and insect problems. The most important of these is sycamore anthracnose, which causes trees to lose many of their leaves during the summer months.

By late summer, some trees will have lost 75 percent or more of their leaves. The disease can spread rapidly during periods of cool wet weather. I expect that this is your problem, and given that we had a very wet spring, the disease will be worse than normal this year. The good news is that it rarely kills trees. Most sycamore trees will carry on through the fall and winter, robustly leaf out again the following spring, and then start the cycle of leaf drop all over again the following summer. The trees are very resilient. Most nurseries and landscapers have stopped selling the sycamore trees but sell a similar hybrid tree called the London plane tree (Platanus x acerifolia). The London plane tree also has some problems, but cultivars such as 'Bloodgood' have some disease resistance.

Most of the shrubs I see listed on native plant lists are quite large. Are there any small native shrubs that will grow well in Baltimore?

Yes, there are several small native shrubs, but if you want a very compact shrub, you may need to select a cultivar of the native species.

Virginia sweetspire (Itea virginica) is native to the East Coast and parts of the Midwest and is generally found in wet areas. However, it is apparently quite adaptable and will grow in fairly dry conditions.

It typically grows up to 5 feet high, but can get much larger. If you want to be sure you are planting a compact plant, I would recommend the cultivar 'Little Henry.' It has attractive white flowers in spring, and excellent purple fall color. Another excellent native plant is summersweet clethra (Clethra alnifolia); however, the species plant will probably get larger than you wish. If you select this plant, you will have to purchase a compact cultivar such as 'Hummingbird.'

'Hummingbird' grows to about 3 feet tall, has very dark green leaves, white summer flowers and yellow fall foliage.

Checklist

1. Check all squash plants for evidence of squash vine borers. Damaged plant stems will appear wilted and have small piles of sawdust-like caterpillar excrement at their base. To control them, carefully slit the affected stems with a razor blade and remove the borers. Pile soil over the wounds.

2. Check all evergreen trees and shrubs for signs of bagworms. Bagworms can be controlled by hand picking, or by spraying with Bt (Bacillus thuringiensis), a microbial insecticide.

3. Remove spent blossoms on flowering annuals and perennials to promote vigorous plant growth and continuous flowering.

Dennis Bishop is an urban horticulture educator for the Baltimore office of the Maryland Cooperative Extension. If you have a gardening or pest problem, you can call the Home and Garden Information Center hot line (8 a.m. to 1 p.m. Monday through Friday) at 800-342-2507. You also can e-mail questions, order publications and diagnose plant problems by visiting the Web site, www.hgic.umd.edu.

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