Goldenrod Galls

Past the hickory tree, where we haven’t mowed since last year, grows a patch of goldenrod. Each fall it lives up to its name, producing bright golden flowers that keep the bumblebees and honeybees busy on warm days.

Look closely, though, and you notice weird things on my plants. Some of them have swellings on the stem – as though they swallowed a golf ball. A few have bunches of leaves that resemble flowers, tucked near the tops of stems. These are galls – deformities caused by insects.

Gall flies, moths and midges are responsible for the deformities in goldenrod. The adult insect lays its eggs on the plants. When the larvae hatch, they chew their way into the stem, irritating the goldenrod. In response, the goldenrod develops a swelling (ball gall) or the tight flower-like cluster that keeps the stem from growing.

When the weather grows cold, the larvae enter a state of suspended animation (diapause) and remain that way until spring, when they resume chewing a tunnel to the gall where they’ll pupate.

Over winter, though, a lot can happen to a gall. Downy woodpeckers and chickadees, hungry for protein-rich snacks, may poke a hole into the gall and chow down on the sleeping larvae.