Japanese Stiltgrass
Microstegium vimineum · Warm-season, Annual, C4 grass
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass
Variety / Cultivar
Wild type, highly adaptive naturalized ecotypes
Hardiness Zones
USDA Hardiness Zones 5 to 9. Highly sensitive to frost and dies back completely with the first hard freeze, leaving behind dense thatch.
About This Grass
A delicate-appearing, sprawling annual grass that forms dense patches. Height typically ranges from 1 to 3 feet when mature. Color is light yellowish-green to medium green, often taking on purplish or reddish tones in late summer or autumn under stress. Texture is medium-fine. Produces slender, spike-like racemes bearing small, paired spikelets.
Blade Characteristics
Blades are lanceolate, flat, 3 to 8 cm long and 4 to 12 mm wide (medium to coarse), with a distinct silvery, offset stripe of reflective hairs down the center of the upper leaf surface. Margins are slightly rough. Vernation is rolled, ligule is a membranous rim, and auricles are absent.
Root System
Shallow, fibrous root system with weak anchorage, making the plants easy to pull up by hand. Nodes along the lower stems easily produce roots where they touch the soil, assisting in rapid lateral spread and dense mat formation.
Growing Information
Origin Region
Native to Asia (Japan, China, Korea, India); naturalized and considered invasive in the Eastern and Midwestern United States.
Growth Habit
Stoloniferous and branching, rooting at the lower nodes to form dense mats or carpets.
Sunlight & Water Needs
Highly adaptable, thriving in both dense shade (where few other grasses survive) and full sun, provided moisture is adequate. Prefers moist, rich soils in floodplains, forests, and disturbed areas. Low drought tolerance.
Mowing & Maintenance
Grows low if continuously mowed, but produces viable seed heads even at very low mowing heights. Generally managed as a weed through hand-pulling, pre-emergent herbicides, or post-emergent selective herbicides. High maintenance due to invasive control needs.
Special Characteristics
Extremely shade-tolerant, excellent at colonizing disturbed shady ground, forest edges, and lawns. Poor wear tolerance compared to turf grasses. Very high weed potential and difficult to eradicate once established due to prolific seed production.
Ecological Information
Introduced accidentally to North America around 1919 (used as packing material for porcelain). Considered a destructive invasive species that outcompetes native understory vegetation, alters soil chemistry, and disrupts natural woodland regeneration. Low wildlife food value; creates heavy thatch that suppresses native flora.