umbrella plant

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

• noun A sedge (Cyperus involucratus syn. C. alternifolius) native to Madagascar and the Mascarene Islands and widely cultivated as an ornamental, having leafless stems with a terminal umbrellalike cluster of long narrow bracts.
• noun Any of various other plants having parts with an umbrellalike form.

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

• noun rhizomatous perennial herb with large dramatic peltate leaves and white to bright pink flowers in round heads on leafless stems; colonizes stream banks in the Sierra Nevada in California
• noun African sedge widely cultivated as an ornamental water plant for its terminal umbrellalike cluster of slender grasslike leaves
• noun late blooming perennial plant of shale barrens of Virginia having flowers in flat-topped clusters