Invasiveness Ranking System for Non-Native Plants of Alaska

Other invasive species in the genus (0–3) 3Polygonum perfoliatum L., P. polystachyum Wallich ex Meisn., andP. sachalinense F. Schmidt ex Maxim. are declared noxious in anumber of American states (Rice 2006, USDA, NRSC 2006).Also Polygonum arenastrum Jord. ex Boreau, P. caespitosumBlume, P. convolvulus L., P. persicaria L., P. lapathifolium L.,P. orientale L., and P. aviculare L. are listed as a weeds in thePLANTS Database (USDA, NRSC 2006). A number ofPolygonum species native to North America have a weedyhabit and are listed as noxious weeds in some American states.Although the latest taxonomy considers these species as membersof three different genus: Polygonum, Fallopia, and Persicaria(FNA 1993+), they are closely related taxa and can be consideredas congeneric weeds.Aquatic, wetland or riparian species (0–3) 3Japanese knotweed often is found near water sources, such asalong streams and rivers, in waste places, utility rights-of-way,neglected gardens, and around old homesites (Beerling et al.1994, Densmore et al. 2001, Seiger 1991).Total for Biological Characteristics and Dispersal 21/25Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 4Japanese knotweed has been planted as ornamental (Densmoreet al. 2001, Seiger 1991).Known level of impact in natural areas (0–6) 6Japanese knotweed has invaded rivers bars in Sitka NationalHistorical Park (Densmore et al. 2001) and has establishedadditional infestations in the Tongass National Forest (Stensvold2000). Large stands have been found along the riverbanks inPennsylvania and Ohio (Seiger 1991).Role of anthropogenic and natural disturbance in5establishment (0–5)Japanese knotweed can establish in native habitats (Stensvold2000, Shaw and Seiger 2002).Current global distribution (0–5) 3Japanese knotweed is native of Japan, Northern China, Taiwan,and Korea. It is now a serious introduced pest in Europe, theUnited Kingdom, North America, and New Zealand. It is widelydistributed in North America (found in at least 42 states andmost Canadian provinces) (Seiger 1991, Shaw and Seiger 2002).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)Japanese knotweed is noxious in California (List B), Oregon (ListB), and Washington (List C) (Rice 2006, USDA, NRCS 2006).Total for Ecological Amplitude and Distribution 23/25Feasibility of ControlScoreSeed banks (0–3)UUnknown. Hybrid seeds of P. x bohemica, stored at roomtemperature, retained viability for 4 years (Beerling et al. 1994).Vegetative regeneration (0–3) 3Japanese knotweed is capable of regeneration from very smallfragments of rhizome (as little as 0.7 grams) (Seiger 1991, Shawand Seiger 2002).Level of effort required (0–4) 4Japanese knotweed is extremely difficult and expensive to control(Child and Wade 2000, Seiger 1991, Shaw and Seiger 2002).Total for Feasibility of Control 7/7Total score for 4 sections 84/97§B-104