Achillea ageratum aka Sweet Yarrow

Achillea ageratum is a herbaceous perennial in the daisy family, Asteraceae. Gardeners also know it as English mace or sweet yarrow. Kew lists its native range as Europe. RHS and Plants For A Future also include Morocco. Its European range includes France, Spain, Portugal, Italy and Croatia. It is not native to Britain or Ireland. Plants For A Future notes some uncertainty about its origin.

This plant forms clumps and loses its leaves in winter. RHS describes plants reaching about 2.6 feet [0.8 metres] tall. Its listed garden height spans 1.6–3.3 feet [0.5–1 metre]. Clumps spread about 0.3–1.6 feet [0.1–0.5 metres] across. They take two to five years to reach full size. The green leaves have divisions or shallow teeth along their edges. Each leaf can reach about 0.16 feet [0.05 metres] long. Many small flowerheads hold clusters of tiny yellow flowers in summer.

Give English mace an open site with full sun. It grows in chalk, loam or sand with good drainage. Acid, neutral and alkaline soils all suit it. RHS lists both well-drained and moist, well-drained conditions. Plants can grow in exposed sites or with shelter. RHS gives it the UK hardiness rating H7. Plants For A Future lists USDA zones 6–9. Divide clumps in spring to make more plants. Cut back untidy leaves at that time. Removing spent flowers may bring more blooms during summer.

English mace suits flower beds, borders and informal cottage gardens. RHS also suggests courtyard, gravel, prairie-style and wildlife gardens. The flowers can be cut for use indoors. Its scented leaves add another reason to grow it. Aphids may attack the plant, and powdery mildew can occur. Plants For A Future does not flag it as weedy. These points make it worth checking both leaves and flowers during growth.

Plants For A Future lists the leaves as edible, raw or cooked. Their mild first taste grows stronger as they are chewed. The aromatic flavour can leave a tingling feeling in the mouth. Use the leaves in mixed salads, soups or stews. They can also flavour potato salad or serve as a tea substitute. Small leaves make picking large amounts a slow task. The source reports no known hazards or medicinal uses. That does not establish safety for pets or every person.