Northern Prairie Wildlife Research Center
Rare in North Dakota, northern greenthread is found only in our most northwesterly counties, and is the only member of the genus found in North Dakota. This is one of only a few plant species whose range is restricted to the northern Great Plains from Wyoming north to the Prairie Provinces. However, some botanists consider the plant merely a variety of a species that ranges southwesterly to Arizona, at elevations up to 8,000 ft.
Northern greenthread is a perennial about 8 inches tall. Stems usually are single, or rarely clustered from creeping rootstocks. The 3-inch-long leaves are mostly basal and once or twice divided into 3-9 thread-like sections. The 1/2-inch-wide, yellow flower heads have no ray flowers, only disc flowers. Heads have bracts with membranous margins. Fruits are tiny achenes about 1/4 inch long.
Look for northern greenthread in dry, native prairie. My few observations suggest that most plants will be found in lightly or moderately-grazed pastures. Some Thelespermas were used to make beverages and dyes by Amerindians of the desert southwest, but I found no mention of northern greenthread in these regards.
Northern greenthread is a member of the sunflower family (Asteraceae). Aster means "star" in Greek, concerning the radiate arrangement of flowers in the heads. This is the largest plant family in North Dakota and most countries with temperate climates. There are only about 10 species in the strictly American genus Thelesperma. The generic name was compounded from the Greek thele, "a nipple," and sperma, "seed," because the achenes have tiny papillae. The specific epithet marginatum means "margined" in botanical Latin. Northern greenthread was described for science by the Swedish-born American botanist Per Axel Rydberg (1860-1931), curator of the New York Botanical Garden and author of several major floras of the American west.