August Plant of the Month: Yarrow

Submitted by the Bath Gamma Garden Club

On a recent trip out west, garden club member Pam Reitz was attracted to the use of yarrow in a native habitat garden at the Denver Botanical Gardens. The plants were buzzing with activity from a variety of pollinators. Previously, she just considered it as a cut or dried flower in a cottage garden.

Common yarrow from Europe and Asia was originally introduced to America in colonial times and has since naturalized throughout the United States. Cultivars of common yarrow have become popular flowering plants for ornamental gardens. Cultivars also extend the range of flower colors to include pinks, reds, creams, yellows and bicolor pastels.

The genus name “Achillea” refers to Achilles, hero of the Trojan Wars in Greek mythology who used the plant medicinally to stop bleeding and to heal the wounds of his soldiers. Native American tribes and early colonists used it to relieve headaches, toothaches, throat irritations, stomach disorders, nausea and fevers. Common yarrow ingredients are found in present-day pharmaceuticals and are used by herbalists.

Yarrow is best grown in lean, dry-to-medium, well-drained sandy loams in full sun. It is suited for hardy Zones 3-9. Typical height and spread are both 2 to 3 feet. The plants tolerate hot, humid summers and drought. Common yarrow blooms white and the flower heads are dome shaped, flat-topped clusters.

As previously mentioned, there are many cultivars in various colors. Wooly hairs cover the stems and leaves of the deeply dissected, fern-like foliage. It is a medium green color that turns to a gray blue that produces a spicy aroma that persists when used in dried arrangements.

Yarrow attracts butterflies and is a primary food source for the blue copper butterflies. This plant also attracts additional beneficial insects including bees, green lacewings, ladybugs, hoverflies and tachinid flies. They are deer resistant.

Yarrow spreads by rhizomes and seeds and can become weedy if not kept in control. It is recommended to divide clumps every 2-3 years. Consider cutting back plants in late spring before flowering to reduce overall plant height and create a bushier clump. You can also cut back to basal foliage after flowering to encourage more flowers. Yarrow typically flowers June through September. The dried flower heads contain thousands of tiny seeds, so remove dried flowers to control reseeding, manage the plant and keep it from spreading aggressively.

Stem rot, powdery mildew and rust are occasional disease problems. Pests include common leaf bugs, flea beetles and spittlebugs.

Yarrow can be used in cottage gardens, seaside gardens, rock gardens, meadows, prairies and naturalized areas. ∞

Photo: Red Yarrow at the Denver Botanical Gardens. Photo by Pam Reitz.