Yarrow grows to 3 feet tall and has no branches except near the top. The leaves are alternate, 3-5 inches long, with many leaflets on each side of the midrib (1- pinnately lobed); and these are further divided into smaller leaflets, giving them a delicate, fernlike, lacy appearance. Flower heads are arranged in large, compact clusters at the top of the stem, each cluster consisting of 1 or more flower heads. The flower head has 20-25 yellowish-white (rarely pink) ray flowers and similarly colored disk flowers.
Achillea millefolium is highly variable and has been treated both as a single species with varieties and as multiple distinct species. A. millefolium is cosmopolitan throughout the Northern Hemisphere. In North America, A. millefolium is a complex of both native and introduced plants and their hybrids.