Japanese Stiltgrass
Microstegium vimineum · Warm-season, Annual, C4 metabolism
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Wetland/Riparian Grass
Variety / Cultivar
Not applicable to this wild invasive species
Hardiness Zones
USDA Hardiness Zones 4-11. It is a summer annual that dies back completely with the first hard frost, leaving behind a thick 'thatch' of tan-colored dead organic matter.
About This Grass
A delicate-looking but aggressive sprawling annual. It features pale green leaves that are short and broad with a distinctive silvery midrib. It can reach heights of 1-3 feet if left unmowed but adapts to low mowing by growing prostrate. Seed heads are slender, terminal spikes or racemes appearing in late summer.
Blade Characteristics
Blades are short (1-3 inches), wide (5-15mm), lance-shaped, and narrowed at both ends. Notable for an off-center, reflective/silvery line of hairs along the midrib. Tips are pointed. Vernation is rolled; ligule is a short, membranous fringe; auricles are absent.
Root System
Shallow, fibrous root system that easily pulls out of the ground. It spreads via rooting at nodes along the stems (stoloniferous growth). Does not form a permanent sod or deep roots, making it susceptible to drought but very fast-growing.
Growing Information
Origin Region
Native to East Asia (China, India, Japan, Korea). Invasive throughout Eastern and Southern United States.
Growth Habit
Stoloniferous and decumbent. It forms dense, sprawling mats by rooting at the nodes (layering) and produces prolific seeds.
Sunlight & Water Needs
Highly shade-tolerant but adaptable to full sun; prefers moist, nitrogen-rich soils but can survive in various conditions. Moderate to high water needs.
Mowing & Maintenance
Maintenance involves suppression rather than cultivation. It can be mowed very low (1-2 inches) to prevent seed production, though it frequently sets seed below mowing heights. Pulling or pre-emergent herbicides are standard for control; it is not cultivated as a desired turf.
Special Characteristics
Exceptional shade tolerance compared to most grasses; extremely high seed production (up to 1,000 seeds per plant); seeds remain viable in soil for up to 5 years; thrives in disturbed areas; allelopathic (alters soil chemistry to inhibit other plants).
Ecological Information
Highly invasive in North America; displaces native vegetation and reduces biodiversity in forest understories; provides little food value for native wildlife; often spreads via contaminated soil or water runoff.