Applied Research
e d a h S Tech f o (Microst inia s g r s i V a egium) — the Crabgr enter, sion C n e t x E h and esearc . Derr, Ph.D., Professor of Weed Science,Hampton Roads Ag. R
By Jeffrey F
J
apanese stiltgrass (Microstegium vimineum), a widespread weed in Virginia, has also been referred to as annual jewgrass, bamboograss, flexible sesagrass, Japanese grass, Mary’s grass and Nepalese browntop. I often call it Microstegium because of the confusion with the various common names. This plant is a shadetolerant C4 summer annual grass. A native of Asia, it was first discovered in the U.S. in 1919 near Knoxville, Tennessee. It apparently it was used as packing material for porcelain from China, and this may have been how it was introduced into the U.S. From this initial infestation, it has spread rapidly and is now widely distributed throughout the eastern United States. Microstegium has moved into New England and the Midwest and has been reported as far west as Texas. This weed occurs throughout Virginia. Microstegium has a large, somewhat circular cotyledon, separating it from other annual grasses. Microstegium has a fibrous root system, with stems that are upright or reclining, and stems can root at the nodes. Plants can reach up to three feet tall. Microstegium pro-
duces tillers that can root into the ground, allowing the plant to spread laterally. Leaves are about four inches long and one-half inch wide and taper at both ends. Most leaves have a distinct white midvein; however, a key identifying feature of this grass is that the midvein does not divide the leaves into equal halves. The seedhead is composed of one to six terminal spike branches. Unlike most C4 plants, Japanese stiltgrass is uniquely adapted to low light conditions. I refer to it as the crabgrass of shade since it grows in moderate to dense shade and spreads laterally by rooting at the nodes, allowing a single plant to cover a significant area. Microstegium is under stress in dry, full-sun environments, so expect to find it primarily in shady areas. Japanese stiltgrass occupies a range of shady, moist habitats including riverbanks, flood plains, damp fields, swamps, woodland thickets, roadside ditches, river bluffs and roadsides. The weed can invade landscape ornamental plantings, turfgrass and vegetable gardens. Microstegium can out-compete native plant species in shaded areas
20 | VIRGINIA TURFGRASS JOURNAL November/December 2016 www.vaturf.org
and, thus, is a major invasive species. Since Japanese stiltgrass is an important weed in Virginia, I have been conducting experiments on the biology and management of this weed.
When does Microstegium germinate? An important question to answer for any annual weed is when does it start to germinate? This information is needed to determine timing of preemergence herbicide applications. I conducted experiments in several locations in southeastern Virginia to determine the germination pattern for this weed. In Virginia Beach, this grass does not flower until the first or second week of October, late for a summer annual grass. So, I expected that it started to germinate later than other summer annual grassy weeds, but that was not the case. Actually, Microstegium started to germinate about a week before smooth crabgrass in my trials. It can start germinating by the second or third week of March in southeastern Virginia, depending on temperature. This year I had Microstegium up to three inches