Achillea ageratum, also known as sweet yarrow, sweet-Nancy, English mace, or sweet maudlin, is a flowering plant in the sunflower family. It is native to southern Europe and Morocco. In the United States the plant is cultivated in the state of New York for its pleasant fragrance and sparingly naturalized in a few places outside its native range.

In the Middle Ages it was used as a strewing herb to repel insects such as moths, lice and ticks and spread a good smell in private rooms. The leaves can be chopped and used raw as a herb, or added with other herbs to soups and stews. Modern uses of the herb include its use as a flavouring, as a dried flower, and as an ornamental herb.

The species was first given a species name by Carl Linnaeus and published in his Species Plantarum 1753. Achillea is a reference to the Greek hero Achilles, who was trained to use herbs by his mentor, the centaur Chiron. The flowers last for a relatively long period, hence the inclusion of ageratum in the species name.

The plant grows to a height of 12 to 18 inches (300 to 460 mm). A hardy perennial, it can be identified by its narrow and serrated leaves, and clusters of small flowers.

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