Yarrow

Achillea is a genus in the aster family, Asteraceae, commonly called yarrow in garden references. Its garden forms range from low, mat-forming alpines to upright herbaceous perennials with finely divided foliage and flat clusters of tiny flowers; species and cultivars vary in size and flower color. [RHS](https://www.rhs.org.uk/plants/achillea) and [NC State Extension](https://plants.ces.ncsu.edu/plants/achillea/) describe these varied garden forms. ## Form and garden use Achillea is useful in borders and cutting gardens, and the flowers can be dried. NC State describes many plants in the genus as 1–4 feet tall and 2–4 feet wide or more; RHS notes that upright flower stems vary from about 30 to 180 cm by species. Flowering is mainly in summer and autumn, with some forms starting in late spring. Basic species commonly have white, cream, or yellow flowers, while cultivated varieties add pink, red, and orange. ## Siting Most Achillea grow best in full sun and well-drained soil, including relatively poor or dry ground. Some, notably A. ptarmica and its varieties, prefer moister soil and partial shade, so check the selected species or cultivar before planting. ## Maintenance Water young plants during dry spells in their first year; most established achilleas tolerate dry periods. Remove faded flower heads to encourage further flowering and limit seed production. Stems can remain over winter for structure and wildlife, then be cut back in early spring. Divide most established clumps every three to five years to maintain vigor. [RHS growing guidance](https://www.rhs.org.uk/plants/achillea/how-to-grow-achillea) describes these care practices.