Yarrow (Achillea millefolium)
Collins, 250; Readers Digest, 340
This is a very common medium height perennial with unusual feathery dark green leaves. The flower heads are stumpy rays of white (and sometimes pink) flowers formed in flat clusters. It is in flower from June to November and enjoys undisturbed grassy places. The legendary warrior, Achilles, was believed to have used the plant to cure wounds made by iron weapons. In Britain, the Anglo Saxons held the same belief.
See also: http://www.botanical.com/botanical/mgmh/y/yarrow02.html