Japanese Stiltgrass
Microstegium vimineum · Warm-season, Annual, C4
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass
Variety / Cultivar
None (Wild type/Invasive species)
Hardiness Zones
USDA Hardiness Zones 4-11; dies back completely with the first killing frost but seeds remain viable for up to 5-7 years.
About This Grass
A delicate-looking, sprawling annual grass that forms dense monocultures. It ranges from 1 to 3 feet in height if left unmowed. It has a pale green or lime-green color and develops a reddish-purple hue in the fall after the first frost.
Blade Characteristics
Blades are short (2-10cm), wide (5-15mm), and lance-shaped with a notable silvery or off-center reflective midrib. The tips are pointed and the surface feels slightly hairy or smooth. Vernation is rolled; ligule is short and membranous with a hairy fringe; auricles are absent.
Root System
Shallow, fibrous root system; spreads primarily via weak stolons and prolific seed production rather than deep roots. Low thatch tendency due to annual lifecycle but creates dense surface debris.
Growing Information
Origin Region
Native to Asia (China, Japan, Korea, India); highly invasive in Eastern/Midwestern United States
Growth Habit
Stoloniferous; sprawling, mat-forming, and decumbent with stems rooting at the nodes
Sunlight & Water Needs
Highly shade-tolerant but also grows in full sun; thrives in moist, disturbed soils but can adapt to various conditions; moderate to high water needs.
Mowing & Maintenance
Not intended for turf; if mowed, height is usually dictated by surrounding lawn (2-4 inches). Maintenance involves removal/control (Low for growth, High for eradication). Prevention of seed-set is critical.
Special Characteristics
Extremely high shade tolerance for a C4 grass; high salt and moisture tolerance; resistant to most deer/wildlife browsing; highly effective at crowding out native vegetation and lawn grasses.
Ecological Information
Highly invasive; reduces plant diversity; alters soil chemistry (pH and nitrogen cycling); provides little food value for native wildlife; often outcompetes native forest-floor species.