By Susan Sharp, NC State Extension Master Gardener^SM  volunteer of Durham County

Many NC gardeners know both the joys and the frustrations of managing landscape beds and woodland areas in the summer.  If we’ve done the planting and maintenance (and if a drought hasn’t done too much damage), plants like black-eyed Susan (Rudbeckia hirta), hyssop (Agastache), sage (Salvia), and Stokes’ asters (Stokesia laevis) are providing color and pollinator interest. On the edges, however, invasive summer weeds will be creeping in.  Some will have grown slowly since spring seeding, while others have volatile spreading habits. Here we look at one of the most challenging: Japanese stiltgrass (Microstegium vimineum).

Late summer appearance of Japanese stiltgrass before flowering – optimum time to control. (Image credit: Andrea Lane CC BY-NC 4.0)

Japanese Stiltgrass – History and Current Status

There are reasons why one of the most popular Horticulture Information Leaflets on the NC State Extension publications website is the one entitled Japanese Stiltgrass Identification and Management. Japanese stiltgrass (Microstegium vimineum), also known as Napalese browntop or bamboograss, is a summer annual in the grass family (Poaceae) that invades both disturbed and undisturbed areas in woodland and landscape settings. Researchers first reported it in the US (Tennessee) around 1919, likely introduced as packing material for fragile items from Asian countries. It now invades at least 26 US states and multiple countries globally, and the NC Invasive Plant Council classifies it as Rank 1 – Severe Threat in NC.

Japanese stiltgrass overgrowth in woodland setting (Image credit: Susan Sharp)

Identification and Growth Habit

Japanese stiltgrass germinates in early spring. Key vegetative identification characteristics include rolled vernation and a short membranous ligule¹. Additionally, the leaf blades are short and broader than most grasses, around 3 inches long and ½ inch across, often with a distinctive silvery stripe of reflective hairs along the midrib. As the season progresses, the stems grow increasingly wiry, turning color from light green to reddish purple through the summer.

Japanese stiltgrass flower in September (Image credit: Susan Sharp)

The flowers are racemes with branched spikes appearing from late August to September, but they often hide within the leaf sheaths. Seeds then easily spread by multiple means carried by awns², including wind, water, people and animals, making pre-flowering control a top priority. Plants will wilt to a light tan shade after frost, but some persist throughout the winter, especially in wooded landscapes.

Japanese stiltgrass awns for seed dispersal (Image credit: Steve Hurst. Provided by ARS Systematic Botany and Mycology Laboratory)

The plant prefers partially shady, moist areas but adapts readily to other conditions and most soil types. It spreads during the growing season by stolons, and each plant can disperse over 1,000 seeds that remain viable for up to four years. Gardeners now find it in woodlands, shaded to partial-sun landscapes, and low-maintenance turf throughout the southeastern US, including Durham County. Unfortunately, it provides little to no food value to animals or insect herbivores, so natural controls on its spread are minimal. If left unchecked, stiltgrass spread can overtake native landscapes in three to five years.

Stiltgrass Control and Management

Controlling Japanese stiltgrass requires persistence and good timing. Mulch is generally ineffective, but denial of light early in the season using blockers like thick cardboard can help in landscape beds. We have experimented with this approach in a home landscape bed this season and have seen less infestation. Hand pulling can help in beds – perfect for meditative weeding, but hard on the gardener’s back. For larger infestations, mowing prior to seeding can reduce spread effectively, and flame weeding works in moist sites when fire hazard is low.

Roadside Japanese stiltgrass mowed in late August (Image credit: Susan Sharp)

Importantly, timing is crucial: gardeners should complete all manual/mowing control measures by mid to late August, before the flowers become visible, to prevent seed production. If removed or mowed before August, the remains can be left as mulch in woodland or shaded areas. Bag all plant debris for disposal if it’s later in summer near the flowering season.

For chemical control, herbicides that target crabgrass will generally control Japanese stiltgrass as well, both pre-emergent and post-emergent. The NC State Horticulture Information Leaflet publication provides details on proper use and timing. The NC Agricultural Chemicals Manual offers additional product-specific guidance. As always, consulting the herbicide label for usage guidance is essential.

Notes

1– In grassy plants, the ligule is a thin outgrowth found on the inner surface of a leaf where the leaf blade meets the sheath that wraps around the stem. It acts as a protective barrier against pests and other stressors for younger leaf tissue. A membraneous ligule is a thin, translucent outgrowth at the junction of the leaf blade and sheath.

2–An awn is a small, usually bristled or barbed projection often used by grassy plants to boost seed dispersal.

Resources and Additional Information

NC State Extension Plant Toolbox: Microstegium vimineum (Japanese Stiltgrass) | North Carolina Extension Gardener Plant Toolbox

NC Invasive Plant Council on Japanese stiltgrass: Invasive Species

USDA PLANTS Database: USDA Plants Database Plant Profile General

NC State Extension Horticulture Information Leaflet: Japanese Stiltgrass Identification and Management | NC State Extension Publications

2026 North Carolina Agricultural Chemicals Manual: 2026 North Carolina Agricultural Chemicals Manual | NC State Extension Publications

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