Ask Mr. Smarty Plants

Coromilla varia, crownvetch, is not a true vetch but a cool season, hardy perennial legume. It was introduced from Europe and southeast Asia during the 1950's as groundcover, and a bank and slope stabilizer. It is intolerant of shade. Because it is a legume, it is also used as a soil rehabilitation agent. A non-native of North America, it is native to Africa, Asia and Europe and has become an invasive species in many states of the United States. Because it is a legume, there would be species of wildflowers that might do well combined with the vetch, such as Castilleja indivisa (entireleaf Indian paintbrush), whose roots go to those of other plants to obtain nutrients. The Lupinus texensis (Texas bluebonnet), being also a legume, fixes nitrogen in the soil on which the Indian paintbrush will draw, so the two wildflowers are frequently seen growing together. However, the downside of the provision of nitrogen in the soil by the vetch is its invasiveness. Being a cool season perennial, while most wildflowers are annuals, it would have a tendency to shade out the sprouting seeds of the wildflowers, and to crowd out the more desirable wildflowers as they try to develop.

If you are trying to establish a wildflower meadow, including the vetch, this would not seem to be very practical. It would be better to first clear the area of the vetch by pulling it out and then seeding the wildflowers in the Fall. The vetch would probably attempt to return, but given a fair start, and with frequent thinning of the vetch, the wildflowers would probably not only make it, but profit from the existence of the nitrogen in the soil provided by the vetch.