Technical Abstract: 'Don' (Reg. No. CV-______, PI _______) a diploid falcata alfalfa (Medicago sativa subsp falcata L.) developed by the Forage and Range Research Laboratory in Logan, Utah, in cooperation with the Utah Agricultural Experiment Station, Utah State University. Recent interest in falcata alfalfa has been high due to its value for increasing the productivity of rangelands. Don was selected for persistence under harsh conditions, uniform yellow flower color, increased seed production and large stature plants. Don traces to PI20725, an original collection made by N.E. Hansen in the Don Province of Russia. Don is significantly more persistent than typical sativa type alfalfas and is meant for use in mixed plantings with grasses either in range or pasture situations typical of the Intermountain region of the Western U.S. In comparative trials, including irrigated and non-irrigatted, where 25 to 50 percent mortality was observed on sativa alfalfas, Don showed no mortality. When used in mixture, the production advantage with tall fescue and meadow brome ranged from 10 to 32 percent. When grown with crested wheat grass on dry rangelands, similar production advantages are expected which will make rangelands more productive. Furthermore, when grown in mixtures with grasses, Don will not dominate; rather it has a low growth habit and stays well below the canopy of most cool season grasses.