Invasiveness Ranking System for Non-Native Plants of Alaska

Aquatic, wetland or riparian species (0–3) 3In its native habitat giant hogweed occurs in forest edges andglades, often at streamsides in montane (Pysek 1991 or Tiley et al.1996, Pysek and Prach 1993, Wright 1984). In Europe its primarycolonization has been along watercourses (Clegg and Grace1974, Pysek 1991). Pysek (1991) reported habitat type wherethe species has been recorded: 42% occurred in a ponds, valleys,riverbanks, road verges, and railway tracks, 41.5% occurred inhuman-made, disturbed habitats including garbage dumps, parks,and gardens, and 15.7% occurred in seminatural habitats such asshrublands, meadows, and forests.Total for Biological Characteristics and Dispersal 22/25Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 0Giant hogweed is not considered an agricultural weed.Known level of impact in natural areas (0–6) 4Giant hogweed’s infestations are located along streams and riversin Washington State (Noxious Weed Control Program 2003).In Scotland giant hogweed invades grasslands and woodlands(Tiley et al. 1996). Giant hogweed was observed in mixedriparian communities, where it became entirely dominant (Cleggand Grace 1974). In the Czech Republic giant hogweed replacesnative vegetation in meadows, shrubs, forest, and forest margins(Pysek 1991, Pysek and Pysek 1995).Role of anthropogenic and natural disturbance inestablishment (0–5)Disturbed habitats such as open disturbed communities are moreeasily invaded by giant hogweed. However, it can also invadeclosed communities such as grasslands and woodlands (Pysekand Pysek 1995, Tiley et al. 1996).3Current global distribution (0–5) 5Giant hogweed is native to the Caucasus Mountains andSouthwestern Asia. It has naturalized throughout central Russiaand Europe. It was introduced to Australia, New Zealand,Canada, and the United States (Tiley et al. 1996, USDA, ARS2005). It has been recorded from arctic and subarctic regions inNorway (Lid and Lid 1995).Extent of the species U.S. range and/or occurrence of5formal state or provincial listing (0–5)Giant hogweed has been documented from Connecticut, Maine,Massachusetts, New Jersey, New York, Oregon, Vermont, andWashington. Giant hogweed is currently on the United Statesfederal noxious weed list. This plant is considered noxious in 12U.S. states, including Oregon and Washington (USDA 2002).Total for Ecological Amplitude and Distribution 17/25Feasibility of ControlScoreSeed banks (0–3) 3Seed longevity can be greater than 7 years (Noxious WeedControl Program 2003).Vegetative regeneration (0–3) 2Resprouting occurs from the base of the plant when floweringstems are cut above ground level. After the stem is cut, a tallcanopy is reestablished within 2 weeks (Tiley et al. 1996, Wright1984).Level of effort required (0–4) 4Control of giant hogweed can include mechanical, chemical, andbiological methods. Plants must be dug out entirely or the rootscut at least 3–4 inches below ground level. Cutting plant stems isineffective. Herbicides have been used on this plant with variableeffectiveness. Grazing by domestic herbivores in springtime maybe effective. A coordinated control program is required over thewhole infestation and surrounding areas, since fresh seed suppliescontinue to spread from uncontrolled plants. A minimum of 5years of an intensive control is required to control giant hogweed(Wright 1984, Tiley and Philp 1992).Total for Feasibility of Control 9/10Total score for 4 sections 81/100§B-45