EDRR Alert: Status Update of Stiltgrass in Maine

EDRR Alert: Status Update of Stiltgrass in Maine

February 24, 2026

Background

Japanese stiltgrass (Microstegium vimineum) is a severely invasive, annual grass originating from southern Asia. Originally introduced to Tennessee in 1919, stiltgrass has seen unbridled spread across the eastern United States over the past century. In Maine, stiltgrass is classified as an early detection and rapid response invasive species (EDRR). EDRR species are recent invaders, meaning they can still be feasibly eradicated from the state. A prolific seed producer, stiltgrass easily invades natural areas and outcompetes many of our native groundcover species. Stiltgrass is also highly allelopathic, meaning it releases organic compounds into the soil that degrade the health of the soil and inhibit the growth of other plant species. As the growing season ends, stiltgrass stems dry out, leaving a thick layer of dry thatch along the forest floor. This introduces a severe wildfire risk to any invaded areas. Due to the countless negative impacts that stiltgrass poses on Maine's natural areas, identifying stiltgrass populations and managing its spread is among the highest priorities for invasive species management in the state.

Identification

There are several characteristics that can be used to identify stiltgrass and distinguish this species from our native grasses in Maine. The most reliable identifying characteristic for stiltgrass can be found on its pale green, alternate leaves. On the upper surface of stiltgrass leaves is a recognizable silvery midrib (central vein running along the length of the leaf). This silver midrib is unique to stiltgrass and is not found on any of Maines native grasses. Additionally, the texture of stiltgrass leaves is extremely smooth or silky. Nearly all of Maines native grasses possess a sticky or grippy texture when passing the leaves between your fingers.

Stiltgrass can also be distinguished from native grasses using its growth form. Mature plants produce aerial roots, or "stilt roots" (the namesake for this species), at lower nodes along the stem that help to prop up the plant. This trait is unique to stiltgrass. Additionally, stiltgrass tends to branch out close to the ground, producing several main stems that may appear to have a sprawling growth habit. This trait is extremely uncommon among Maines native grass species.

Stiltgrass in Maine

Since 2020, Maine Natural Areas Program (MNAP) staff have actively managed stiltgrass populations in 3 Maine towns: York/Cape Neddick, Sanford, and Georgetown. With consistent annual management, stiltgrass population densities at these sites have significantly declined. In 2025, MNAP increased statewide outreach, detailing the severity of unchecked populations of this invasive species. Mainers from across the state responded in droves, sending in reports of potential stiltgrass populations on their property. With the help of conservation organizations, landowners, and concerned citizens, MNAP confirmed 4 new populations of stiltgrass in South Berwick, Westport Island, West Gardiner, and Blue Hill.

Newly identified populations will all undergo initial management during the 2026 growing season, while control will continue on the older sites. However, the search for stiltgrass is not over. Identifying populations of stiltgrass before they are well established is the key to slowing the spread of this severely invasive species, protecting our natural areas, and ultimately eradicating this species from the state of Maine. If you think you have discovered a stiltgrass population, please email [email protected] with pictures of identifying characteristics and specific location details.

Stiltgrass in Maine Video

Supporting documents