Japanese Stiltgrass
Microstegium vimineum · Warm-season, Annual, C4
Grass Family
Poaceae, Panicoideae, Tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Riparian/Wetland Weed
Variety / Cultivar
Native genotype (highly invasive)
Hardiness Zones
USDA Zones 4-11; survives as an annual seed bank; germinates in spring, flowers in late summer, dies with first frost.
About This Grass
A delicate, sprawling annual grass that forms dense, low-growing mats. It is pale green with a distinctive silvery stripe down the midvein. Reaches 1-3 feet tall but often reclines; produces small, inconspicuous terminal and axillary spikes.
Blade Characteristics
Lance-shaped blades, 1-3 inches long; medium width (5-15mm). Key feature is a silvery, reflective line along the midrib (slightly off-center). Tips are pointed; vernation is rolled; ligule is short and membranous.
Root System
Shallow, fibrous root system; weak and very easy to pull; stems root easily at lower nodes (layering), allowing it to colonize quickly but lacks true rhizomes.
Growing Information
Origin Region
Native to Asia (China, India, Japan, Korea); invasive throughout Eastern and Midwestern US
Growth Habit
Stoloniferous and decumbent (sprawling); stems often root at the nodes (nodes appear swollen)
Sunlight & Water Needs
Shade tolerant (very high), also grows in partial sun; prefers moist soils, floodplains, and disturbed woodland edges; moderate to high water needs.
Mowing & Maintenance
Maintenance involves eradication rather than cultivation. Hand-pulling, mowing before seed set (late summer), or post-emergent herbicides are common controls. High maintenance for removal.
Special Characteristics
Exceptional shade tolerance; high seed production (up to 1,000 per plant); seeds remain viable for 3-5 years; allelopathic (alters soil chemistry to suppress other plants).
Ecological Information
Invasive; outcompetes native forest floor flora; provides poor wildlife value; disrupts nitrogen cycling in woodland ecosystems; often spreads via foot traffic and deer.