cotton grass

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various sedges of the genus Eriophorum, chiefly of wet places in northern temperate and cold regions and bearing one or more conspicuous tufts of cottony bristles.

from The Century Dictionary.

• noun A panic-grass, Panicum insulare, bearing cottony or silky hairs on its spikelets.
• noun The popular name of plants of the genus Eriophorum, natural order Cyperaceæ.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun any sedge of the genus Eriophorum; north temperate bog plants with tufted spikes