yarrow, any of about 115 species of perennial herbs constituting the genus Achillea in the family Asteraceae, and native primarily to the North Temperate Zone. They have toothed, often finely cut leaves that are sometimes aromatic. The many small white, yellow, or pink flowers often are grouped into flat-topped clusters.
Some species are cultivated as garden ornamentals. The dried leaves of sneezewort (A. ptarmica) are used to make a sneezing powder, and parts of yarrow or milfoil (A. millefolium) have been used for snuff and tea.