Pennsylvania is the only state that has designated an official state beautification and conservation plant (made official in 1982). First discovered in 1935 on Mr. Gift's farm in Pennsylvania, Penngift Crownvetch (Coronilla Varia L. Penngift) is valuable as food for livestock, erosion control , and nitrogen feeding of the soil. The Pennsylvania Department of Transportation has planted it along roads throughout the state. Penngift Crownvetch produces attractive rose, white, or pinkish-white flowers from June to September.

Crownvetch is a spreading, long-lived, winter-hardy, drought- tolerant, herbaceous legume with angular stems that grow to a height of 2 to 3 feet during the blooming period, after which the plant forms a dense mat about a foot deep. Its principal use is for erosion control, soil building, and ground cover. It is especially valuable for holding banks along highways. The stand improves with age and gradually chokes out other weeds. It is also used for its ornamental value on steep banks and hillsides.

Source:

Clover and some relatives
Pennsylvania - Symbols: PA Historical & Museum Comm.

Links:

Benefits of Crownvetch as a Living Mulch: Penn State U
Crownvetch's Role in Vegetation Management: PennDOT
State Flowers & Plants - 50 States List
National Flower