Exotic and Invasive Plants of Alaska
Non-native invasive plants displace native vegetation, degrade wildlife habitat and negatively affect human health, the economy and the environment. Geograhic isolation and harsh winters have protected Alaska from large-scale plant invasions in the past. Recently, however, many noxious weeds of the lower 48 states have arrived and are spreading within the state.
Exotic plants are species that are not native to Alaska but have been introduced either purposely or accidently through the activities of man. They may also be called non-native, alien or introduced plants.
Invasive plants are species capable of spreading rapidly throughout certain habitats.
These are not mutually exclusive concepts. Exotic plants are not necessarily invasive and native plants can become invasive under some circumstances. Many of our Alaskan plants are quite opportunistic.
For the most part, the assessments of nativity made by floras treating Alaska and neighboring areas were used to develop the following checklist of exotic plants, particularly Hult\xe9n 1968, Cody 1996, Douglas et al. 1998-2001 (see taxonomic references) and the USDA PLANTS database. In many cases plants deemed native to North America in the PLANTS database are exotic to Alaska. Some plants on the list are not present in Alaska as far as we know, but have been spreading northwestward in North America and are included here to remind people to watch out for them. To find out where plants on the list have been found consult the University of Alaska Museum of the North Database for herbarium specimens and the AKEPIC database for observations. Many of the plants on the list are agricultural or ornamental plants brought purposely to Alaska and pose little if any threat of invading natural landscapes. Still they are clearly exotics and most of them have been found at least once in places where they were not planted.
The checklist is in alphabetical order by family, with genus and species alphabetical within families. Names accepted by the Herbarium of the University of Alaska Museum of the North are in uppercase. Synonyms are in lower case and are indented below the appropriate accepted name as well as being cross-referenced in their expected alphabetical position. Currently the checklist includes only the Asteraceae. Criticisms, comments and questions regarding the checklist can be sent to Alan Batten.
For a ranking of the level of invasiveness of our most common weeds, see the Weed Ranking Project.