Japanese Stiltgrass: An Invasive Threat to the Shenandoah Watershed
Common name: Japanese Stiltgrass
Scientific name: Microstegium vimineum
Native to East and Southeast Asia, Japanese Stiltgrass was introduced to the United States and first documented in Tennessee in 1918. It has since spread across more than 24 eastern U.S. states. Its dense, mat-like growth reduces biodiversity and changes habitat structure, negatively impacting forests, timber resources, scenic areas, and agricultural lands. (Fryer, 2018; USDA Forest Service, 2010; Penn State Extension, 2020).
IDENTIFICATION
Japanese Stiltgrass is a fast-growing annual grass that can spread both along the ground and upright, depending on its environment. Its thin, bamboo-like stems can reach up to 3.5 feet tall or sprawl long distances. The leaves are short, lance-shaped, and distinguished by a shiny, silvery midrib of fine hairs on the upper surface, while the lower surfaces have soft hairs. Japanese Stiltgrass blooms from late summer to fall, producing many small flowers (spikelets) that can self-fertilize. After frost, the green foliage fades to a light tan color and the stems persist through winter, remaining visible during the dormant season (Fryer, 2018; NC State Extension, n.d.; Native Plant Trust, 2024).
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org.
HABITATS
Japanese Stiltgrass thrives in a wide range of environments, including shaded, moist, and disturbed areas such as floodplain forests, wetlands, upland woods, forest and stream edges, roadsides, and gardens. Its adaptability to both low and high light and mild frost conditions allows it to colonize areas rapidly. This grass often takes hold in areas disturbed by natural or human activities, such as logging, construction, flooding, or foot traffic, and once established, it quickly spreads into nearby, less disturbed habitats (NC State Extension, n.d.; Native Plant Trust, 2024).
SIMILAR SPECIES
Japanese Stiltgrass is easily confused with native grasses like Whitegrass (also known as Cutgrass) but there are several key differences between them. Whitegrass is a perennial with longer, narrower leaves and a less noticeable midvein, while Stiltgrass is an annual with broader leaves marked by a shiny midrib. Another way to tell them apart is by their roots, Japanese Stiltgrass has a weak, shallow root system and can be pulled up easily, whereas Whitegrass forms strong underground rhizomes that help it return year after year (Native Plant Trust, 2024; Penn State Extension, 2020).
https://katymorikawa.com/floyd-native-plants-2024/
INVASIVE CHARACTERISTICS / ADVANTAGES
Japanese Stiltgrass colonizes disturbed streambanks and riparian areas where flooding or erosion have exposed bare soil (Fryer, 2018; Pennsylvania Sea Grant, 2025). In this environment, Stiltgrass crowds and displaces native plants and young trees that are critical for stabilizing streambanks and natural recovery processes (Fryer, 2018; Pennsylvania Sea Grant, 2025; GrowIt BuildIT, 2024). Its dense mat growth prevents both woody and herbaceous native species from establishing and regenerating, resulting in a decline of plant diversity and the loss of long-term streambank structure and ecosystem function (Fryer, 2018; GrowIt BuildIT, 2024).
The presence of Japanese Stiltgrass also alters soil chemistry by raising soil pH and modifying nutrient cycling rates (Fryer, 2018; Pennsylvania Sea Grant, 2025). These changes inhibit native seed germination and alter forest and streambank composition, leading to reductions in native plant regeneration (Fryer, 2018). By rapidly blanketing the ground, shifting soil conditions, and outcompeting native vegetation, Japanese Stiltgrass destabilizes forest regeneration and streambank ecosystems throughout the Shenandoah watershed (Fryer, 2018; Shoemaker et al., 2009).
REMOVAL / REMEDIATION STRATEGIES
Effective management of Japanese Stiltgrass includes hand-pulling smaller areas before it begins to seed, as the roots are shallow and the plants are easy to remove. Mowing is also effective when done before seed production, as mowing after the seeds mature can facilitate its spread. If the plants have already produced seeds, it is recommended to bag the plants after removing them to prevent seed dispersal. Applying herbicide can also be useful for larger infestations, and after removal, replanting native vegetation can help prevent regrowth. It’s also important to prevent soil disturbance and clean the equipment to minimize its reinfestation (NC State Extension, n.d.; Penn State Extension, 2020).
https://dnr.wisconsin.gov/topic/Invasives/fact/JapaneseStiltGrass
Japanese stiltgrass poses a significant threat to the ecological health of the Shenandoah Watershed by outcompeting native plants and altering habitat structure. Effective management and ongoing monitoring are essential to limit its spread and protect biodiversity. By understanding its impacts and implementing control strategies, stakeholders can help preserve the integrity of this vital ecosystem for future generations.
References
Fryer, J. L. (2018). Ecological risk screening summary: Japanese stiltgrass (Microstegium vimineum). U.S. Fish & Wildlife Service. https://www.fws.gov/sites/default/files/documents/Ecological-Risk-Screening-Summary-Japanese-Stiltgrass.pdf
GrowIt BuildIT. (2024, December 21). A beginner’s guide to Japanese stiltgrass. https://growitbuildit.com/japanese-stiltgrass-microstegium-vimineum/
NC State Extension. (n.d.). Microstegium vimineum (Asian stiltgrass, Chinese packing grass).https://plants.ces.ncsu.edu/plants/microstegium-vimineum/
Native Plant Trust. (2024). Microstegium vimineum (Japanese stiltgrass). Go Botany. https://gobotany.nativeplanttrust.org/species/microstegium/vimineum/
Penn State Extension. (2020, July 15). Japanese stiltgrass. https://extension.psu.edu/japanese-stiltgrass/
Pennsylvania Sea Grant. (2025, October 16). Japanese stiltgrass fact sheet. https://seagrant.psu.edu/resources/resource-item/japanese-stiltgrass-fact-sheet/
Shoemaker, D., et al. (2009). Diversity declines in Microstegium vimineum (Japanese stiltgrass). Biological Conservation, 142(7), 1523–1532. https://www.sciencedirect.com/science/article/abs/pii/S0006320709000408
USDA Forest Service. (2010, December 31). Microstegium vimineum. USDA Forest Service. https://www.fs.usda.gov/database/feis/plants/graminoid/micvim/all.html
