Bulletin #2529, Maine Invasive Plants: Japanese Stilt Grass (Chinese Packing Grass), Microstegium vimineum (Grass Family)
Developed by the Maine Natural Areas Program and University of Maine Cooperative Extension
Threats to Native Habitats
Japanese stilt grass is a highly aggressive species capable of colonizing a wide variety of habitats. It is successful in both high and low light conditions and in moist to moderately dry soils. It readily invades natural areas, replacing native species with nearly monospecific stands. It spreads opportunistically following disturbance, especially where canopy openings have resulted. In Pennsylvania, defoliation from gypsy moths allowed this species to colonize vast expanses of upland forest. Infestations of Japanese stilt grass change the habitat of the forest floor, making it less hospitable for some ground-nesting bird species.
Japanese stilt grass is a relatively weak-stemmed annual that grows from one to three feet in height. Its hairless stems have a sprawling growth habit, are usually branched, and often root at the lower nodes. Each stem has many alternately arranged, lance-shaped leaves, which are pale green and up to three inches in length. The leaves have a silvery stripe of reflective hairs down the middle of the upper surface. Spikes with numerous quarter-inch-long, flattened, trapezoid-shaped flowers emerge from the top of the plant and from the branch axils in late summer. Identification becomes easier in the fall when the plants develop a light purplish tinge. This species is similar in appearance to the uncommon native white grass (Leersia virginica), which is found in Maine along the margins of some streams and rivers. Consult an experienced botanist for help in identifying Japanese stilt grass.
Stilt grass occurs in a wide variety of settings including floodplains, forested wetlands, lowland forests, upland forests, successional fields, forest edges, thickets, and utility corridors. Infestations spread most rapidly in disturbed areas such as flood-scoured stream banks, abandoned or seldom-used roadbeds and utility corridors that receive annual mowing. It colonizes undisturbed habitats more slowly but expands opportunistically in areas with canopy openings or soil disturbances.
The native range of this species includes tropical eastern and central Asia. It is thought to have reached North America in the early 1900s when the plants were used as packing material for fragile trade goods. It is currently established in nearly all the states east of the Mississippi River and along the gulf coast, with the notable exception of northern New England. Observations indicate that it is slowly spreading northward.
As with all invasive plants, prevention is the best method of control. Avoid transferring seeds of stilt grass to new locations on clothing or otherwise. As stilt grass is a weak-rooted annual, new or relatively small infestations can be pulled up by hand. Effective hand-pulling will require follow-up visits for several seasons to remove plants emerging from seeds stored in the soil. Larger populations can be mowed or weed-whacked, which should be done when plants are mature but seeds have not set. Mowing before seeds have set will prevent plants from sending up new shoots and making new crops of seeds. For more extensive infestations, a systemic herbicide (i.e., glyphosate), or an herbicide specific to annual grasses may be a better choice. If applying herbicides to plants in wetland areas, use a product designed for use in wetlands. Use herbicides responsibly and follow the manufacturer’s directions. Contact the Maine Department of Agriculture for information on restrictions that apply to the use of herbicides. Consult a licensed herbicide applicator before applying herbicides over large areas.
Mandy, T. “Element Stewardship Abstract for Microstegium vimineum.” The Nature Conservancy in collaboration with the International Network of Natural Heritage Programs and Conservation Data Centers. Arlington, VA: Natural Heritage Databases, 2000.
Swearingen, J.M. “Japanese Stilt Grass: Microstegium vimineum (Trin.) Camus.” Weeds Gone Wild: Alien Plant Invaders of Natural Areas. Plant Conservation Alliance’s Alien Plant Working Group.
Gleason, H.A. and A. Cronquist. Manual of Vascular Plants of Northeastern United States and Adjacent Canada, Second Edition. New York: New York Botanical Garden, 1991.
For more information or for a more extensive list of references on invasive species contact:
Department of Conservation
#93 State House Station
Augusta, ME 04333-0093
University of Maine Cooperative Extension
495 College Avenue
Orono, ME 04469
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