Vigorous trailing legume (Coronilla varia), native to the Mediterranean but widely grown in temperate areas as a ground cover. It has fernlike leaves and clusters of white to pink flowers. The sturdy roots are useful in binding the soil of steep slopes and roadside embankments. As a legume, crown vetch draws nitrogen from the air, trapping it in the roots, and thus improves soil fertility. It dies back to the crown each fall in cold areas, resuming growth in spring. Cutting the plant back in the fall or early spring encourages quick growth.