Japanese Stiltgrass
Microstegium vimineum · Warm-season, Summer Annual, C4
Grass Family
Poaceae, subfamily Panicoideae, tribe Andropogoneae
Grass Category
Invasive/Weed Grass
Variety / Cultivar
None (wild species / invasive)
Hardiness Zones
USDA Zones 4-11; annual life cycle allows it to survive northern winters as seeds.
About This Grass
A delicate-looking, sprawling annual grass that forms dense, pale green carpets. It can reach heights of 1-3 feet if unsupported. It features a distinctive silvery, off-center midrib and matures to produce terminal or axillary racemes in late summer/autumn. The leaves turn a pale reddish-brown in the fall.
Blade Characteristics
Leaves are short (2-10 cm long), lanceolate, and relatively wide (5-15 mm) with a distinctive silver reflective midrib that is slightly off-center. Tips are pointed; vernation is rolled. The 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 weak stolons that root at the nodes but does not produce true rhizomes. It produces a massive seed bank rather than a dense perennial sod.
Growing Information
Origin Region
Native to Southeast Asia (China, Japan, Korea, India); highly invasive in Eastern United States
Growth Habit
Spreading (decumbent) growth habit; stoloniferous and rooting at the nodes (culms) to form dense mats
Sunlight & Water Needs
Highly shade-tolerant but thrives in full sun; prefers moist, nitrogen-rich soils but is adaptable to various moisture levels and soil types (pH 4.8 to 8.2).
Mowing & Maintenance
Usually not cultivated. If present in lawns, it should be mowed frequent and low to prevent seed head formation. Hand pulling is effective due to shallow roots; pre-emergent herbicides in early spring are primary control methods. Maintenance level: Very High (as a weed).
Special Characteristics
Extreme shade tolerance (as low as 5% sunlight); prolific seed production (up to 1,000 seeds per plant); highly invasive; outcompetes native groundcovers; deer unpalatability helps it dominate forest floors.
Ecological Information
Introduced invasive species; provides very low wildlife value and significantly degrades native biodiversity by suppressing native seedling recruitment and altering soil chemistry/cycling.