Density of seed of three species of locoweed, salt milkvetch [Astragalus lentiginosus var. salinas (Howell) Barneby], Lambert locoweed (Oxytropis lambertii Pursh. # OXRLA), and white locoweed (O. sericea Nutt ex. T.&G. # OXRMA) in the soil was determined at four locations in New Mexico, Wyoming, and Utah. Seed density ranged from 50 to 2820/m2. Greater than 77% of the seed were viable as determined by tetrazolium tests. Longevity of white locoweed seed was determined by sewing seed into nylon mesh packets and returning them to the site of origin in northwestern Utah. Greater than 50% of seed buried 1 cm deep in the soil were still present after 6 yr, but only 33% of seed placed on the surface remained. Germinability of the buried seed was less than 5%, but an average of 14% of seed placed on the soil surface germinated each year. Viability of retrieved seed ranged from 89 to 99%.
