How do you identify it?
The grass has long, alternately arranged leaves. Its leaf blades are broad and short, and leaves are lance-shaped. It is bright green in color with spikes of flowers.
Why is it invasive?
Japanese stiltgrass spreads into natural areas and can persist under a closed canopy in the forest. It is common in shaded and moist disturbed areas like wetlands. Still, it can invade drier uplands with full sunlight, and it can spread to undisturbed areas. Seeds can spread by animals, flooding and footwear. It can create dense stands and out-compete native plant species. Additionally, it can persist in grazed areas because deer avoid it.
How can you manage it?
Hand-pulling and other mechanical controls like mowing can be effective if done before the grass produces seed. Herbicides may also be used before seeds are produced. For example, small amounts of glyphosate can be effective. When herbicides are used, monitoring should be completed in the following years. The NC Forest Service has more detailed herbicide information. Make sure to follow all label instructions.
Invasive Species Leaflet IS-4 Japanese Stiltgrass (North Carolina Forest Service)
The spread of M. vimineum poses a particularly severe threat to natural areas because this plant is adapted to low light conditions and is able to grow and produce seeds underneath a closed forest canopy. Because of the seriousness of its threat to natural areas, preventing the introduction of M. vimineum and early control of new infestations should be the utmost priority for land managers.
Insiduous and Formidable Japanese Stiltgrass (Blue Ridge PRISM)
Because of its delicate bright green foliage and slender stems, Japanese stiltgrass (Microstegium vimenium) appears deceptively harmless. Even where the grass has been established for only a few years, it forms a dense groundcover that smothers native plants and prevents regeneration of forests and fields. This trait dramatically decreases the scenic beauty, timber value and wildlife habitat of the land that stiltgrass invades.
Japanese Stiltgrass Control (Missouri Department of Conservation)
Hand pulling Japanese stiltgrass can damage native plants and disturb the soil, which provides opportunities for other invasive plants. To cause less damage to native broadleaf plants, use grass-selective herbicides with active ingredients fluazifop-p-butyl (such as Fusilade) or sethoxydim (such as Poast) in July and August before seeds are produced.
Japanese Stiltgrass (Penn State Extension)
Japanese stiltgrass (Microstegium vimineum) is a widespread invader of woodlands and a prolific seeder with a sprawling growth habit. It is often found growing along trails and roads where it quickly spreads to the forest understory. The tiny seeds are carried on shoes, cars, ATVs and logging and road-maintenance equipment. Once introduced, it is extremely difficult to remove from a site.
Field Guide to the Identification of Japanese Stiltgrass (Alabama Cooperative Extension)
Japanese stiltgrass (Microstegium vimineum) is an aggressive invader of forest lands throughout the Eastern United States. Infestations can impact the diversity of native species, reduce wildlife habitat and disrupt important ecosystem functions. Stiltgrass is considered one of the most damaging invasive plant species in the United States.
Weed Alert: Act Now on Japanese Stiltgrass (Blue Ridge PRISM)
The weeks before it flowers and sets seed is the time to control Japanese stiltgrass, Microstegium vimineum. A single Japanese stiltgrass plant can produce up to 1,000 seeds that can remain viable in the soil for at least three years. The seeds are spread by animals, rain runoff, soil and human foot traffic. Take action to help minimize seed production and prevent stiltgrass from achieving a wider footprint.
Japanese Stiltgrass (video, N.C. Tree Farm Program)
Tree Farmer Rhett Davis talks about Japanese Stiltgrass in North Carolina’s forests.