Crown vetch (Coronilla varia) works well as a ground cover for wide open spaces, but it can become invasive in a small landscape. A single plant can spread 6 square feet, and plants may self-seed, overtaking native plants and other landscape plantings. Another ground cover might be a better choice for your yard. Crown vetch does have many good qualities, including pink-and-white blooms from late spring to early fall, attractive foliage all season, and no serious pest problems. It's often used along highways because it is also salt-tolerant.