yarrow, a plant of the genus Achillea, perennial herbs of the family Asteraceae (aster family), native to north temperate regions. Several species are cultivated as ornamentals for their flat-topped clusters of flowers and scented foliage. The common yarrow (A. millefolium), also called milfoil, has white flowers in the wild, but there are also pinkish varieties in cultivation. Yarrow was a love charm of high repute, and in Greek mythology Achilles (hence the generic name) used the plant to heal the wounds of his soldiers and to stop bleeding. Native Americans also used the plant medicinally, particularly as a treatment for earache. The use of yarrow in folk medicine is based on its apparent anti-inflammatory and coagulatory properties. Some yarrows are among the plants imparting a disagreeable taste to milk when grazed by cows. Water milfoils are unrelated freshwater aquatic perennials of the genus Myriophyllum, sometimes grown in aquariums and ponds; Eurasian water milfoil is a pest species in some U.S. inland waters. Yarrow is classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.

Any of about 80 species of perennial herbs that make up the genus Achillea in the composite family, native mainly to the northern temperate zone. Some species are cultivated as garden ornamentals. They have toothed, often finely cut, sometimes aromatic leaves. Many small white, yellow, or pink flowers are often grouped into flat-topped clusters, which can be dried for winter bouquets.

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