A Wet Season Can Take a Bite Out of You

By Adrian Higgins
Thursday, July 17, 2008

If you garden long enough in one place, you realize that no two growing seasons ever match up.

Some years, there are subtle changes: a rare late frost that punishes those who jumped the gun or a tropical storm that brings down an old tree.

In other periods, you wonder if you are living in the same place. This year, for example, with a spring and summer that have delivered abundant rainfall when plants are programmed to grow their most. The contrast to last year's punishing drought makes it all the more extraordinary.

Last fall, I came across gardeners who were spending hundreds, even thousands of dollars keeping water running through hoses as a form of survival gardening. Now, after about 30 inches of rain so far this year, it's a jungle out there. Hoses remain coiled like snakes.

This is mostly positive news. The elusive quest for a green lawn in summer seems attainable, and a lush garden makes its owner look and feel good. There are a few downsides, however.

When the weather turned hot a month ago, virtually every fungal and bacterial disease encouraged by warm, wet conditions made an appearance.

There's fire blight on apples and pears, including the Bradford and other ornamental varieties of the callery pear. This bacterium produces dieback in stems and leaves, yielding a classic shepherd's crook at the stem end and a blackening as if the branch had been burned. Experts have come up with a clever way of pruning out the dead branches in a way that stops the disease from forming in lower branches. It's a two-step process that initially leaves a stub. See the Maryland Home and Garden Information Center Web site, http://www.hgic.umd.edu.

I'd say that black spot in roses is becoming a problem, but only in roses that still have their leaves. Weather-induced or not, in May and June there was an outbreak of rose slugs the likes of which have rarely been seen. The pest, which is the larvae of a sawfly, munches on the underside of rose leaflets until it chews right through. "More [damage] than I have ever seen in all the years I've been doing this," said David Yost, a horticulturist at Merrifield Garden Center, who runs a diagnostic plant clinic for customers. He also reports unusual numbers of bagworms and wonders if the mild winter is a factor.

But the drumbeat is more of foliage problems. This has been a banner year for leaf spot on redtip photinia as well as anthracnose disease on sycamore leaves. The black-eyed Susans in my garden are robust, but the lower leaves are heavily marked by a fungus named Septoria. I sometimes remember to spray them in May with a lime-sulfur fungicide (this prevents the disease from gaining hold), but I didn't this year. Must have been singing in the rain.

My tomato vines are just showing signs of early blight, a disease that turns the lower leaves black and yellow. Mulching the bed will help, as will removing the infected leaves and avoiding overhead watering.

As Yost points out, most of these diseases are not going kill their hosts and are part and parcel of a rainy year. However, perennials and herbs that favor free-draining soil, typically those with silver or gray leaves, will croak in wet clay soil, from root or crown rot. Heavy organic mulches increase the risk.

Another problem, if it is a problem, is the sheer amount and weight of fruit and flowers on shrubs and trees. Peach tree boughs are groaning in spite of repeated thinnings of developing fruit, said Matt Davenport, manager of Hollin Farms in Delaplane, Va. Cherry trees are similarly fruitful, the corn is "phenomenal," he said, and the hay meadows produced two to three times the normal amount in May and June. His crews are getting ready to cut a second crop of hay in late July, a resource unavailable in last year's drought.

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