Invasiveness Ranking System for Non-Native Plants of Alaska

Impact on Higher Trophic Levels (0–10) 7A total of 27 species of birds and 46 mammals are known to usealfalfa (Graham 1941). Alfalfa is consumed by most big gameanimals, including moose and mule deer (Kufeld 1973, Leach1956). Many small mammals, including marmots, mice, andground squirrels graze alfalfa. Waterfowl such as the Americanwigeon and mallards eat the leaves, flowers, or seeds. Seeds arealso consumed by rodents, rabbits, and upland birds. Alfalfa is asource of nectar and pollen for insects (Stanton 1974, Graham1941) and it is particularly attractive to solitary bees (Carlsonpers. obs.). Dabbling ducks (mallards, blue-winged teals,northern pintail, northern shovelers, and American wigeons)will nest in alfalfa stands (Klett et al. 1984). Undisturbed alfalfafields provide food and cover for a variety of birds, includingsharp-tailed grouse, American bitterns, marsh hawks, short-earedowls, and passerines (Duebbert et al. 1981). Alfalfa is a host fornumerous pathogens (Sullivan 1992).Total for Ecological Impact 13/30Biological Characteristics and Dispersal ScoreMode of Reproduction (0–3) 3Alfalfa reproduces by seed only (USDA 2002). The mean numberof seeds produced by an individual plant has been documented at5,320 (Stevens 1932).Long-distance dispersal (0–3) 2Alfalfa seeds are large and not easily dispersed. Herbivores likelyfacilitate the spread of the plant’s seeds (Duebbert et al. 1981,Kufeld 1973, Leach 1956).Spread by humans (0–3) 3Alfalfa is cultivated worldwide and is used in erosion-controlprojects, for rangeland and wildlife habitat restoration, and forhay production. The utility of the plant probably contributes to itsspread (Klett et al. 1984, McLean et al. 1971).Allelopathic (0–2) 0Alfalfa is not allelophathic (USDA 2002).Competitive Ability (0–3) 3Alfalfa seedlings have faster root extension and greater total rootlength than other perennial legumes (Bell 2004). Establishedalfalfa plants can be very competitive (Sullivan 1992).However, in Saskatchewan ranchlands seeded with alfalfa wereoutcompeted by aspen and prickly rose (Rosa acicularis) (Bowes1981)Thicket-forming/Smothering growth form (0–2) 1Alfalfa can grow very densely from 3 to 5 feet high and can betaller than surrounding forbs and grasses (USDA 2002, Royerand Dickinson 1999).Germination requirements (0–3) 2Although seed germination can be inhibited by the presenceof pine and juniper litter (Sullivan 1992), seeding undisturbedrangelands and woodlands can be successful (MAFRI 2004).Other invasive species in the genus (0–3) 3Medicago sativa ssp. falcata (L.) Arcang., M. lupulina L.,M. polymorpha L., and M. minima (L.) L. (USDA 2002, Royer andDickinson 1999, Hultén, E. 1968).Aquatic, wetland or riparian species (0–3) 0Alfalfa has established along roadsides, in waste areas, (Hitchcockand Cronquist 1973, Hultén 1968) and active and abandonedagricultural fields (Royer and Dickinson 1999). It is not known toinvade wetlands or riparian communities.Total for Biological Characteristics and Dispersal 17/25Ecological Amplitude and Distribution ScoreHighly domesticated or a weed of agriculture (0–4) 4Alfalfa is one of the most widely grown forage crops in the world(Powell and Bork 2004, Sullivan 1992). A number of agriculturalvarieties have been developed.Known level of impact in natural areas (0–6) 1Modest impacts of Medicago sativa ssp. sativa have been observedin sagebrush deserts of the Great Basin (Carlson pers. obs.)Role of anthropogenic and natural disturbance inestablishment (0–5)Alfalfa readily establishes on natural rangelands and burned areas(MAFRI 2004). This species failed to establish in areas disturbedby grazing (Sullivan 1992, Smith 1963). In Alaska this taxon doesnot persist (J. Conn pers. com.).Current global distribution (0–5) 5Alfalfa originates from Southwestern Asia. It was first cultivatedin Iran, and now has a worldwide distribution as an agriculturalcrop (Sullivan 1992).Extent of the species US range and/or occurrence offormal state or provincial listing (0–5)It is planted in all 50 states and is widely planted in Canada(USDA 2002, Sullivan 1992).Total for Ecological Amplitude and Distribution 16/25Feasibility of ControlScoreSeed banks (0–3) 3A study of crop and weed seed longevity showed that seeds ofalfalfa remain viable for 20 years in soil (Lewis 1973).Vegetative regeneration (0–3) 2Alfalfa is capable of sprouting from stumps. In Utah, increasedherbivore access was correlated with increased lateral shootssprouting (Rosenstock and Stevens 1989).Level of effort required (0–4) 2Control measures have not been developed due to the value ofthis plant as an agricultural crop. It is known to persist on fieldsthat were previously cultivated for forage or hay (Royer andDickinson 1999). Alfalfa is susceptible to herbicides (Bowes1982, Cogliastro et al. 1990).Total for Feasibility of Control 7/10Total score for 4 sections 53/90§15B-79