Brown Leaves in Summer
What’s the deal?
At the Thursday Deale Farmers Market, a number of Bay Weekly readers have asked what is causing so many trees to turn brown. This year the browning of leaves started in late June and has progressed rapidly. The browning has nothing to do with drought, which some people blame.
The black locust leaf miner is responsible.
Because of the rapid spread, it appears that the insect over-wintered and had an early start on this year’s foliage. During the most severe winters, black locust leaf miners are killed. The next year, you can follow the progressive invasion northward from the more southern states. In those years, browning of black locust trees generally does not become visible until late July or early August.
In the Garden
Black locust is a very fast-growing tree and, like most fast-growing trees, has a short life. However, it differs from other short-lived trees in that its wood is very resistant to decay. Farmers have long used black locust for making fence posts, which last 30 to 40 years in the ground. The wood of most fast-growing trees — such as willow, tree of heaven, poplar and so on — decays quickly. The wood of black locust is also different in that it burns slowly and generates very intense heat but leaves few ashes. The wood of the other fast-growing trees burns very quickly and leaves behind lots of ash.
Beekeepers like black locust because the trees’ flowers appear at a time when most native species have either already flowered or are about to flower. With the flowers come an abundance of nectar and pollen.
On the downside, black locusts produce an abundance of seeds, creating a weed problem in lawns, pastures and cultivated fields. Month-old seedlings can be controlled by mowing. However, allow the seedling to grow a full year and you’ll have to either grub out the roots or use a herbicide. It is not uncommon to see year-old seedlings that have grown three to five feet tall.
Ask Dr. Gouin your questions at firstname.lastname@example.org. All questions will appear in Bay Weekly. Please include your name and address.