Microstegium spp.

stiltgrass

SunPart Shade – Full Shade – Full Sun

Overview

Microstegium spp. is a genus of sprawling annual grasses in the family Poaceae, native to tropical and temperate Asia. The genus is known chiefly through Microstegium vimineum, Japanese stiltgrass, a shade-tolerant annual that has become a widespread invasive weed in eastern North America. Plants produce thin, branching, reclining stems 12-40 inches (30-100 cm) long that root at the lower nodes and form sprawling mats. The lance-shaped leaves are pale green, 1-3 inches (2.5-8 cm) long, with a thin line of silvery hairs slightly off the center of the blade. Slender flowering spikes appear in late summer and autumn, and plants also set hidden self-pollinating flowers low on the stems, producing large amounts of seed. As an annual, the whole plant dies with the first hard frost, leaving thatch that suppresses other low vegetation. M. vimineum grows most densely in moist, shaded ground along streams, floodplains, trails, and disturbed woodland, where it can carpet the soil. It is listed as a noxious or invasive weed in many eastern U.S. states.

Native Range

Microstegium spp. is native to tropical and temperate Asia, including Japan, Korea, China, India, and Southeast Asia. M. vimineum was introduced to North America in the early twentieth century and is now naturalized across much of the eastern United States.

Suggested Uses

Microstegium spp. is not planted as an ornamental and is managed mainly as an invasive weed of woodlands and waterways. It appears in ecological and restoration studies as a model of shade-tolerant plant invasion. Where it occurs, control rather than cultivation is the usual aim.

How to Identify

Identify Microstegium spp. by its thin, sprawling, branched stems that root at the nodes and its pale green, lance-shaped leaves marked with an off-center line of silvery hairs. Slender flowering spikes rise in late summer and autumn. The reclining stilt-like stems and silvery leaf midline separate M. vimineum from native woodland grasses, which usually grow more upright.

Appearance

Size & Dimensions

Height1' - 3'4"

Width/Spread1' - 3'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~8 weeks

Summer Fall

Flowering spikes appear from late summer into autumn, generally August to October. Plants also produce concealed self-pollinating flowers low on the stems, so seed is set even without open flowering. A single plant can shed hundreds of seeds that remain viable in the soil for several years.

Detailed Descriptions

Flower Description

Green to purplish

Foliage Description

Pale green with silvery midline

Growing Conditions

Sun Requirements

SunPartial Shade SunFull Shade SunFull Sun

Requires 1-8 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 Range5.0 - 7.0(Neutral)

357912

Soil Types

loam silt clay

Drainagemoist

Water & Climate

Water Needs

Medium

Care & Maintenance

Care Guide

As a shade-tolerant annual, M. vimineum grows in part to full shade on moist, fertile soils, though it also persists in sun where moisture is steady. It occupies disturbed, damp ground such as stream banks, floodplains, ditches, and trail edges. Seedlings emerge in spring, sprawl through summer, and die with the first frost. The genus spreads rapidly by seed carried on water, footwear, machinery, and animals. Dense stands shade out low-growing native plants and build a smothering layer of dead stems. Bare, moist, disturbed soil is colonized fastest.

Pruning

Cutting or mowing close to the ground in late summer, before seed matures, reduces the season's seed set. Because the plant is a shallow-rooted annual, hand-pulling removes whole plants from moist soil. Repeated removal over several years is needed to exhaust the seed bank.