dyer's greenweed

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

• noun A small shrub (Genista tinctoria) in the pea family, native to Eurasia, having clusters of yellow flowers that yield a dye.

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

• noun small Eurasian shrub having clusters of yellow flowers that yield a dye; common as a weed in Britain and the United States; sometimes grown as an ornamental