One of the Fastest-Spreading Forest Weeds Found In 23 States

Contact: Marc Imlay | 301-442-5657 |

One of the Fastest-Spreading Forest Weeds Found In 23 States
Photo: James H. Miller & Ted Bodner, Southern Weed Science Society,

ANNAPOLIS, MD (Sept. 5, 2003) – Before people used styrofoam peanuts as packing material, they used fabric, wood shavings or dried plant leaves and stems to protect breakables in shipping. One of the worst invasive weeds in the Mid-Atlantic states, Japanese Stiltgrass (Microstegium vimineum) probably was introduced as packaging for delicate Oriental porcelain in the early 1900s. Now present in 23 states, and one of the fastest spreading forest weeds, Microstegiumis considered by land managers as a potentially time-consuming and expensive problem.

Microstegium can thrive in as little as five percent of normal sunshine, so it is well adapted to the shady forest floor, especially in moist areas such as floodplains. It spreads rapidly following disturbance, forming monocultures, where it shades or crowds out native species.

The Maryland Invasive Species Council (MISC) lists Microstegium as September’s “Invader of the Month.” MISC seeks to educate the public on the problems associated with invasive species and how to control and prevent introductions.

Microstegium is widely recognized as a problem by biologists and natural resource managers because it negatively affects a variety of native species. “Microstegium already covers five to 10 percent of New Jersey,” said Marc Imlay, vice-president of the Maryland Native Plant Society, “and in Maryland the worst is yet to come.”

Microstegium is an annual grass that looks like miniature bamboo. It germinates in April and grows through the summer, up to 3 feet tall. The pale spring-green leaves are about 3-inch elongated ovals, with blunted points at each end, branching alternately from the wiry stem. Although there is one native forest grass that looks similar, Microstegium can be distinguished by the stripe of silvery hairs down the midrib of the leaves. Careful observers will note that this silvery stripe is not directly in the center of each leaf, but curves slightly to one side, so that the leaves are divided into two unequal sections. Almost any trail in moist woods this time of year will have Microstegiumgrowing along it.

One of the Fastest-Spreading Forest Weeds Found In 23 States
Japanese stilt grass infestation in Maryland. Photo: Michael Ellis

Microstegium flowers are inconspicuous, delicate sprays of greenish-white at the tips of the plants. They appear beginning in late summer and continue into September and October, when seeds are produced. Microstegium can spread quickly during the growing season by stem rooting where the plants bend over to touch the soil, and by seed. Microstegium seed is probably spread in water currents and by animals walking through patches. One plant can produce up to 1,000 seeds, which can survive in the soil for three to five years.

Natural enemies that keep Microstegium under control in its native Asian range are not present in the U.S. "However, this invader can be easily controlled,” said Imlay. A multi-year program of hand weeding, mowing or weed wacking before flowering, as well as torching, or spraying with an herbicide will work. Because seeds remain dormant, it takes several years to get rid of Microstegium, even if each year’s plants are prevented from going to seed. With everyone’s help, this is one invasive species that Maryland can do without.

For more information on Microstegium, contact Marc Imlay, 301-442-5657,