Polygonum
From Salish Sea Wiki
Polygonums are a varied mix of introduced rhizomatous shrubs and native and introduced forbs. Native forbs are uncommon in the lowland Salish Sea, introduced Eurasian field weeds like Polygonum persicaria are a much more common species in damp soils. Polygonum cuspidatum (Japanese knotweed), P. x bohemicum (bohemian knotweed) and P. sachalinense (giant knotweed) is an important introduced rhizomatous shrub species that is increasingly covering areas in the Salish Sea. While we may ultimately consider reintroduction of native Polygonum, most of this page will likely be focused on the massive challenge of how to manage the introduction of Japanese knotweed.
Polygonum cuspidatum (Siebold & Zucc.), Japanese Knotweed
- USDA Plants Page - https://plants.usda.gov/home/plantProfile?symbol=POCU6
- Listed as class B noxious weed in 1995.
Control Notes
- root starvation by cutting or covering, and spraying are recommended by various sources.
- Recommendations are potentially conflicting, "all plant material should be removed and properly disposed of" and "frequent, repeated cutting of plants over many years can eventually kill the plant" and "it is prohibited to transport plant parts" potentially increasing cost and professionalizing management. It is unclear how regulation controls in situ treatment.
- https://invasivespecies.wa.gov/priorityspecies/japanese-knotweed/
- Snohomish County Page https://snohomishcountywa.gov/2012/38232/Knotweed-Stem-Injector
- Washington State Noxious Weed Control Board listing provides a long list of fact sheets by different sources of information - https://www.nwcb.wa.gov/weeds/japanese-knotweed
