Fallopia japonica

Photo courtesy Joseph DiTomaso

Synonyms: Polygonum cuspidatum; Reynoutria japonica, Fallopia baldschuanica

Common names: Japanese knotweed; Mexican bamboo

Fallopia japonica (=Polygonum cuspidatum) (Japanese knotweed) is a perennial forb/herb (family Polygonaceae ). Plants grow vigorously and create dense colonies that exclude other vegetation. Established colonies are extremely difficult to eradicate. It inhabits disturbed moist sites, roadsides, riparian and wetland areas. Plants typically grow in open, sunny areas on moist soils in cool temperate climates. There is very little of this species in California, but it is spreading rapidly in the Northwest and has been a major problem in the southern and northern US, as well as Europe.

Rating: Moderate

Cal-IPC Resources

  • Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
  • Cal-IPC News - Our quarterly newsletter. Each issue is available as a pdf.
  • Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium.
  • Don't Plant a Pest! - Select your region to find non-invasive alternatives to ornamental species. Also see our statewide brochure on trees.

Other Resources

Symposium Presentations

None for this species.

Cal-IPC News Articles