Dryland seedling emergence of basalt milkvetch (Astragalus filipes) and western prairie clover (Dalea ornata) under different planting seasons and seed treatments

Abstract

Basalt milkvetch and western prairie clover are native perennial legumes distributed in the northern Great Basin and Columbia River Plateau of North America, with recent germplasm releases providing seed for revegetation. Although seed germination studies have identified scarification requirements for both species, and additional cold stratification for Astragalus filipes, no research has been conducted to optimize the likelihood of seedling emergence on rangeland sites. In this study, we planted both species in 3 locations in the northern Great Basin over 3 y. Seeds were planted in both fall and spring seasons, with emergence measured each June. For both species, there was variation in seedling emergence success across locations and years, with the Powell Butte, Oregon, location providing the highest emergence and the 2011–2012 winter season leading to the highest emergence. For A. filipes, the greatest seedling emergence occurred with fall plantings with scarified seed because of a need for cold stratification and a slow germination rate. For Dalea ornata, because of its hard seedcoat yet rapid germination, the greatest seedling emergence occurred with spring plantings with scarified seed. Our data indicate a need for scarifying seed for both species, but planting A. filipes in fall and planting D. ornata in spring.