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Origin
Japanese knotweed, native to Japan, was introduced into the United Sates before 1890 as an ornamental perennial and for erosion control because of its long, stout rhizomes.
Known Distribution
Japanese knotweed is found from Maine to Wisconsin and south to Louisiana. It is also found scattered throughout the Midwest and some western states.
Habitat
Japanese knotweed is most often found near water sources, low lying areas, waste places, utility right of ways and surrounding old home sites. Its wide range of habitat is due to its ability to tolerate a wide range of conditions including deep shade, high temperatures, high salinity and drought.
Ecology
Japanese knotweed spreads quickly and forms a dense thicket that excludes native vegetation and alters natural ecosystems. Japanese knotweed also poses a significant threat to riparian areas.
Identification
This herbaceous perennial is a member of the buckwheat (Polygonaceae) family. It can grow to over 10 feet tall with smooth stems.
Leaves are broad and oval to somewhat triangular and pointed at the tip and can be as much as 6 inches long by 3 to 4 inches wide.
Flowers, fruits and seeds: This perennial produces minute greenish-white flowers in branched sprays during the summer which produce small winged fruits containing tiny, triangular seeds.
Dispersal: Japanese knotweed is capable of reproducing both by seed and vegetatively with long, stout rhizomes. It is commonly dispersed by water, wind, as a contaminant in fill dirt and on the soles of shoes.
Prevention and Control
Japanese knotweed can be hand pulled if care is taken to remove all roots and runners. Care should also be taken to prevent the transportation of seeds or rhizomes on shoes and clothing. Glyphosate and triclopyr herbicides may be applied to freshly cut stems among hardy populations.
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