dog fennel

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

• noun A weedy plant (Eupatorium capillifolium) in the composite family, native to the southeast United States and having pinnately divided leaves and long clusters of greenish flowers.

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

• noun weedy plant of southeastern United States having divided leaves and long clusters of greenish flowers
• noun widespread rank-smelling weed having white-rayed flower heads with yellow discs