Rarities include root crops salsify and scorzonera (vegetable oyster), both like thin parsnips. One unique class of stilbenoid derivative was first isolated from "Scorzonera humilis". Well-known species include the edible black salsify ("Scorzonera hispanica"). Scorzonera humilis, the viper's-grass, is a perennial plant. Some "Scorzonera" species contain lactones, including the sesquiterpene lactones known as guaianolides. Flavonoids found in "Scorzonera" include apigenin, kaempferol, luteolin, and quercetin. Scorzonera tau-saghyz is a species of "Scorzonera", in the family Asteraceae. Scorzonera is a genus of flowering plants in the dandelion tribe within the daisy family.