Japanese Stiltgrass
Microstegium vimineum · Warm-season, Annual, C4 grass
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass, Wetland/Riparian
Variety / Cultivar
Wild type, no cultivated varieties
Hardiness Zones
Thrives in USDA Hardiness Zones 5 through 9, exhibiting high cold tolerance for an annual as seeds overwinter successfully.
About This Grass
An annual grass with a delicate, sprawling habit, growing 1 to 3 feet tall. It has a light to medium green color, often turning purplish in autumn before dying back in frost. Forms dense, tangled patches. Seed heads are slender, spike-like racemes appearing in late summer.
Blade Characteristics
Blades are flat, relatively short (1 to 3 inches), and medium-to-wide (5 to 15 mm), with a distinctive silvery, off-center stripe of reflective hairs down the middle of the upper surface. Tips are pointed, vernation is rolled, and ligules are membranous and fringed with hairs.
Root System
Shallow, fibrous root system with weak anchorage, making it easy to pull up by hand. Spreads primarily by prolific seed production and secondarily by rooting at lower stem nodes.
Growing Information
Origin Region
Native to Asia (China, Japan, Korea, India, Malaysia); naturalized extensively in the eastern United States
Growth Habit
Stoloniferous and branching; sprawls and roots at the nodes to form dense, expansive mats
Sunlight & Water Needs
Highly shade tolerant, but also grows in full sun. Prefers moist to wet soils, frequently found in floodplains, damp woods, and disturbed shaded areas. Low drought tolerance.
Mowing & Maintenance
Acts as a weed in lawns and natural areas; can be controlled by frequent low mowing before seed set in late summer. High maintenance required to eradicate.
Special Characteristics
Extremely invasive, crowds out native understory vegetation, low wear tolerance, highly adaptable to low-light conditions, poor forage value for livestock.
Ecological Information
Considered a severe invasive weed in North America, displacing native flora in forests and riparian zones. Provides little wildlife value while disrupting forest regeneration.