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Invasive Species: Japanese Knotweed
*Established in Michigan*
Report this species:
Use the Midwest Invasive Species Information Network (MISIN) online reporting tool
- Or - download the MISIN smartphone app and report from your phone - MISIN.MSU.edu/tools/apps/#home
- Perennial, herbaceous shrub that can grow from 3-10 feet high.
- Hollow stalks are persistent through winter, looks similar to bamboo.
- Stems have a fine white coating that rubs off easily.
- Flowers arranged in spikes near the end of the stem are small, numerous, and creamy white in color.
- Flowers bloom in August and September in Michigan.
Photo courtesy of Jan Samanek, State Phytosanitary Administration, Bugwood.org.
Photo courtesy of Nanna Borcherdt, Sitka Conservation Society, Bugwood.org.
Photo courtesy of Randy Westbrooks, Invasive Plant Control Inc., Bugwood.org.
Habitat: Japanese knotweed can be found along roadsides, wetlands, wet depression, woodland edges and stream or river banks. Full sun conditions are preferable, although this plant can tolerate some shade and a wide range of soil and moisture conditions.
Native Range: Asia.
U.S. Distribution: Japanese knotweed has been introduced to most of the contiguous U.S. Florida, Alabama, Texas, New Mexico, Arizona, Nevada, Wyoming and North Dakota are the exceptions.
Local Concern: Japanese knotweed grows very aggressively in disturbed areas. It excludes native plants by light limitation, nutrient cycling alterations and allelopathy (releasing toxic or inhibiting chemicals to suppress the growth of potential competitor plant species).
Best Control Practice Guide for Japanese Knotweed This document provides in-depth information about Japanese Knotweed in the State of Michigan including identification, distribution, management, and control options.