The flowers of redroot buckwheat (Eriogonum racemosum) is one of the many species of plants that the gray hairstreak larvae will feed on.  Although this plant has green basal leaves that are visible in the spring, this plant doesn't usually bloom until late summer.  When it does, througout much of its distribution, the gray hairstreak will utilize this plant.  (At the same time, in many places in the Rocky Mountains, gray hairstreaks will also use Astragalus spp. that are in bloom during the spring months.)