Common Name: Japanese Knotweed
Alternate Names: Japanese bamboo, Mexican bamboo, Japanese fleece flower, crimson beauty, Reynoutria, Hancock’s curse
Scientific Names: Polygonum cuspidatum Siebold & Zucc., synonym Fallopia japonica (Houtt.) Ronse Decr.
Related Species: Giant knotweed (Polygonum sachalinense F. Schmidt ex Maxim.) and hybrids
Any person, corporation, business or other retail entity distributing Japanese and/or giant knotweeds for sale within the state must have information directly affixed to the plant or container packaging that it is being sold with, indicating that it is inadvisable to plant this species within 100 feet of a water body or its designated flood plain, as defined by Minnesota Statute 103F.111, Subdivision 4. View Minnesota Noxious Weed Law for more information.
Japanese knotweed is native to eastern Asia and was imported to England in the mid-1800s as an ornamental. It was prized and planted in many famous gardens. In the late 1800s, it was brought to the United States and was planted in gardens and used for erosion control along roadways and embankments. Japanese knotweed escaped cultivation, overtook desirable vegetation and was recognized as a problem by the early 1900s and now inspires dramatic headlines such as “The largest female on earth could strangle Britain” in the London Daily Telegraph.
Japanese knotweed can be found in sunny areas along roadsides and in riparian areas such as river banks. Knotweeds thrive in a wide range of soil types. Some homeowners have intentionally planted Japanese knotweed in their landscapes.
Rhizomes allow Japanese knotweed to spread quickly and aggressively, although seed is sometimes produced. In North America, Japanese knotweed plants produce only female flowers and therefore cannot produce seed without a pollen source. However, both giant knotweed and bohemian knotweed (a fertile hybrid) can produce both female and male flowers and may provide a pollen source for Japanese knotweed plants where they coexist, resulting in viable seed production. New colonies can form from very small rhizome or root fragments that are moved by natural means such as waterways as well as by human activities that move soil such as construction. Japanese knotweed is very persistent after establishment. It is widespread in the eastern US and reported in 41 states. There are multiple, isolated infestations in Minnesota. View Japanese knotweed distribution in Minnesota.
Japanese knotweed forms tall, dense thickets that shade out and displace native vegetation, degrade habitat for fish and wildlife, can alter waterways, and facilitate erosion and flooding. Knotweed growth through pavement cracks and along paved surface edges can result in damaged pavement.
MDA Noxious Weed Program
County Ag Inspectors