any of a genus (Eriophorum) of grasslike plants of the sedge family, with flower heads resembling tufts of cotton, common in northern bogs
See cotton grass in American Heritage Dictionary 4
noun
Any of various perennial grasslike plants of the genus Eriophorum native chiefly to wet places in northern temperate and cold regions and bearing at maturity one or more conspicuous tufts of cottony bristles.