Invasiveness Ranking System for Non-Native Plants of Alaska

Role of anthropogenic and natural disturbance in3establishment (0–5)Hawkweeds readily grow in cleared areas in forests. Mowingpromotes flowering and spreading of stolons. However,populations often establish in remote mountain meadows andforested habitats with moderate levels of natural disturbance(Rinella and Sheley 2002). Orange and meadow hawkweeds havebeen established in native communities with natural disturbancesin Kodiak, Juneau, and Valdez (P. Spencer pers. com., M.Shephard pers. com.).Current global distribution (0–5) 3Orange hawkweed originates from the British Isles, southernScandinavia, west to Russia, and south to the Mediterranean.Meadow hawkweed is indigenous to Northern, Central, andEastern Europe. Hawkweeds now are also established in EastAsia, the United States, Canada, and New Zealand (Hultén 1968,Rinella and Sheley 2002).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)Hieracium aurantiacum listed as a noxious weed in BritishColombia, Colorado, Idaho, Minnesota, Montana, Quebec, andWashington. H. caespitosum is considered a noxious in Idaho,Montana, Oregon, and Washington (Invaders Database System2003, USDA 2002).Total for Ecological Amplitude and Distribution 19/25Feasibility of ControlScoreSeed banks (0–3) 3Seeds of hawkweeds are viable up to 7 years (Rinella and Sheley2002).Vegetative regeneration (0–3) 2The hawkweeds are capable of spreading by rhizomes and stolonsand adventitious root buds (Rinella and Sheley 2002).Level of effort required (0–4) 3Mechanical control procedures are generally not successful;digging, grazing, or tillage can stimulate the growth of new plantsfrom fragmented roots, stolons, and rhizomes. Orange hawkweedcan be controlled with herbicides. The site should be monitoredfor several years for plants growing from root fragments and fromseed bank. Small, isolated populations are more easily controlled(Rinella and Sheley 2002).Total for Feasibility of Control 8/10Total score for 4 sections 79/100§B-48