The public is asked to look out for two severely invasive plants: Stiltgrass (Microstegium vinimeum) and Perennial Pepperweed (Lepidium latifolium). Stiltgrass leaves alternate along the stem and have a silvery midrib. Photo courtesy of the Maine Department of Agriculture, Conservation and Forestry

AUGUSTA — Biologists from the Maine Department of Agriculture, Conservation and Forestry are asking for the public’s help looking out for two severely invasive plants: Stiltgrass (Microstegium vinimeum) and Perennial Pepperweed (Lepidium latifolium).

The plants are only known from a handful of sites in Maine, and the goal is to eliminate them from the state. The public can help by looking for the plants and reporting any suspected locations.

Stiltgrass is an annual grass that takes over the forest floor. Stiltgrass thatch builds up and makes it difficult for native trees, shrubs, and wildflowers to establish and grow. The thatch also raises fire risk.

Infestations grow rapidly, since each plant can produce up to 1,000 seeds spreadable by moving water, deer, contaminated soil, dirty boots, or dirty equipment. Two locations of Stiltgrass were detected for the first time in Maine in 2020.

Perennial Pepperweed, also known as Perennial Pepperwort, is an herbaceous plant that can take over sensitive habitats in salt marshes and sandy beaches. These are rare habitats in Maine and home to rare wildlife. When Perennial Pepperweed takes over, it can make the habitat unsuitable.

Perennial Pepperweed can also grow in roadsides, riverbanks, and freshwater marshes. There are dense infestations of Perennial Pepperweed in Massachusetts, but only a handful of sites are known in Maine and New Hampshire.

The most valuable assistance is to review the MNAP Web Gallery at maine.gov and GoBotany website, gobotany.nativeplanttrust.org, to become familiar with the plants and then email suspect photos and location descriptions to [email protected], or map the location with pictures in the online mapping tool iMapInvasives at maine.gov.

This tool allows users to view other mapped locations, explore invasive species, and set up email alerts for areas or species of concern.

Newly-detected Stiltgrass or Perennial Pepperweed should be removed to keep these invasive plants from damaging Maine’s forests and wetlands. DACF will offer support and guidance to affected landowners.

Perennial Pepperweed has alternate leaves that are smaller toward the top of the plant. Clusters of small white flowers bloom in late June to mid July. Photo courtesy of the Maine Department of Agriculture, Conservation and Forestry

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