The scientific name for Crown vetch is Coronilla varia. A tough and aggressive ground cover mostly used for covering steep slopes, it has a love/hate relationship within the plant world. It's disliked because of its aggressive nature, but loved in places where little else will grow or where erosion on steep slopes is a problem. In the transportation industry, crown vetch is used on highways all across North America.
Coronilla is a fast growing, thickly spreading ground cover with few pest or disease problems. It reaches a mature height of 18 inches and self sows by spreading seed. It can be quite vigorous, bordering on invasive, and for that reason care must be taken when selecting a planting location.
Crown vetch prefers well-drained and slightly acidic soils. However, since it is a plant in the Leguminosae or bean family, it can manufacture its own nitrogen and will grow well on poor sandy soils. Place the plant 10 to 14 inches on center in a sunny location, ideally where it can spread and not cause a problem. Once established it is extremely drought tolerant in hardiness zones 4 to 9.
Flowers appear from late spring-early summer to fall in shades ranging from dark pink to bright white. The flowers are 1/2 inch long blooming in dense clusters. Since crown vetch is in the bean family, the flowers are small and pea-like, similar to what you would see on a sweet pea vine.
Crown vetch is a deciduous ground cover and in the late fall and winter months it will go dormant and drop all leaves. In spring and summer leaflets appear in oblong to oval-shaped pairs. The entire leaf is finely textured with a feathery appearance.
There are three varieties of crown vetch: emerald, penngift and chemung. Some varieties offer brighter green leaves or different flower colors. The cultivar emerald shows a richer leaf color than the straight species. Chemung and emerald are known to be taller and hardier than penngift.
Since crown vetch fixes its own nitrogen it must be inoculated before planting. Inoculation provides a specific bacteria required to create nitrogen and can be obtained where the seeds are purchased. Sugar water makes the inoculum adhere to the seed.
Once crown vetch is established it is easy to maintain by mowing once a year to remove dead twigs, branches and debris. This will rejuvenate the plant and create a dense lush stand. Keep in mind that trash and debris collect between the tangled branches and larger debris can be difficult to remove. Hand collecting trash might be necessary from time to time.