Xyris difformis, the bog yelloweyed grass, is a North American species of flowering plant in the yellow-eyed-grass family. It is native to the eastern and southern United States, eastern and central Canada, and Central America.Xyris difformis is a perennial herb up to 90 cm (3 feet) tall with grass-like leaves up to 50 cm (20 inches) long, and yellow flowers. VarietiesXyris difformis var. curtissii (Malme) Kral - Belize, coastal states of USA from Texas to VirginiaXyris difformis var.