Any of about 25 species of spring-flowering perennial herbaceous plants that make up the genus Trillium in the family Melanthiaceae, native to North America and Asia. Whorls of oval leaves, flower parts, and fruits are arranged in groups of three. Each solitary white, greenish-white, yellow, pink, or purple flower is borne on a short stalk that arises from the whorl of leaves. Many species are cultivated in wildflower gardens. Wild trillium (also called wake-robin or birthroot) is a protected species.