marsh elder

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

• noun Any of several North American herbs or shrubs of the genus Iva of the composite family, often growing in salt marshes and having nodding, greenish flower heads.

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

• noun any of various coarse shrubby plants of the genus Iva with small greenish flowers; common in moist areas (as coastal salt marshes) of eastern and central North America