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Microstegium vimineum

Japanese stiltgrass

SunFull Sun – Part Shade – Full Shade

Overview

Microstegium vimineum is a sprawling annual grass reaching 1-3.5 feet (30-100 cm) long, with thin, branching stems that lean on other plants or trail along the ground and root where the lower nodes touch soil. The pale green lance-shaped leaf blades are 1.5-3 inches (4-8 cm) long and 0.2-0.6 inch (5-15 mm) wide, marked by a glossy off-center silvery line of reflective hairs along the midrib, a key identifying feature. From late summer into fall it produces slender spike-like flower stalks 1-3 inches (2.5-8 cm) long, bearing both open wind-pollinated flowers and hidden self-pollinating ones, and a single plant can shed hundreds to over a thousand seeds. The seed stays viable in the soil for several years. It grows in shade and partial sun on moist, disturbed ground such as woodland floors, trail edges, floodplains, and ditches, forming dense mats that smother low native plants. It is a widespread invasive grass in eastern North America, spread along trails, streams, and roadsides. The whole plant dies with the first frost, leaving thatch that suppresses other seedlings.

Native Range

Microstegium vimineum is native to temperate and tropical Asia, including Japan, Korea, China, and India, where it grows in moist, shaded habitats. It was introduced to North America in the early 1900s and has spread across much of the eastern United States.

Suggested Uses

Microstegium vimineum has no garden use and is listed as a noxious or invasive weed in many eastern states. It is the target of removal in woodlands, parks, and natural areas, where it displaces native ground flora. Land managers track and control it along trails, streams, and roadsides where it spreads.

How to Identify

Identify Japanese stiltgrass by its thin, sprawling, pale green stems that root at the lower nodes and its short lance-shaped leaf blades 1.5-3 inches (4-8 cm) long. A glossy, off-center silvery stripe of reflective hairs runs along the midrib of each blade, the clearest field mark. Slender flower spikes appear in late summer and fall, and the loose, branching mats it forms resemble a miniature bamboo.

Appearance

Size & Dimensions

Height1' - 3'6"

Width/Spread1' - 3'

Colors

Flower Colors

green

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Slender flower spikes appear from late summer into fall, generally August to October, shortly before the plant dies. It carries both open wind-pollinated flowers and closed self-pollinating ones, so it sets seed even in deep shade. Seed drops through fall and can remain viable in the soil for three to five years.

Detailed Descriptions

Foliage Description

pale green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade SunFull Shade

Requires 1-6 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam clay silt

Drainagemoist

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

Microstegium vimineum is an invasive weed rather than a cultivated plant, and management focuses on control instead of care. It grows in moist, shaded to partly sunny sites with disturbed soil and tolerates a wide pH range of about 5.5-7.5. As a shallow-rooted annual, it is pulled or cut low before the late-summer flowers set seed, which over several years depletes the seed bank. Cutting or mowing in early fall, just before flowering, limits seed production. It dies completely at first frost. Because the seed persists for years, repeated removal across multiple seasons is needed to clear an area.

Pruning

Pruning does not apply to this annual grass. Cutting or mowing low in late summer, before the flower spikes set seed, is the main control method. Hand-pulling works well because the shallow roots release easily from moist soil.