Another method of producing selenium is to farm selenium-gathering plants such as milk vetch. Rare and endangered plants include Heckert's pepperweed and Ferris' alkali milk vetch. The flowers are Chinese milk vetch, which are the prefectural flower. In Vermont, "Vincetoxicum nigrum" crowds out the endangered species Jesup's milk vetch ("Astragalus robbinsii" var. Near the North Forth American River is Whitney's milk vetch ("Astragalus whitneyi" var.