Stiltgrass has an Achilles’ heel

Q: We have been living here for over 40 years, and we’ve noticed over the last few years an increase of a 2-foot-high grassy plant taking over in parts of the woods. The plant turns out to be Japanese stiltgrass. It’s considered to be a seriously invasive plant in the eastern U.S. From talking with neighbors, it seems few have ever heard of this plant.

A: Stiltgrass, also known as basket grass or microstegium, is one of the most troublesome weeds that I know. It is particularly at home in moist spots, and shade makes it happy as well. One plant can produce hundreds of seeds. The plant, however, has an Achilles’ heel: it germinates from seed in the spring. Since it is an annual plant, it can be controlled by preemergent chemicals. Products that contain dithiopyr, pendimethalin, or prodiamine will prevent microstegium seed from germinating. Since seeds germinate throughout the summer, two applications (mid-February and early May) are appropriate. For a heavy infestation, a third application in July might be warranted. Read and follow label instructions, particularly the requirement that they be kept away from water.