Yarrow (Achillea) is a resilient perennial known for its vibrant flowers and fern-like foliage, blooming from late spring into fall. Pruning is an effective practice that contributes to the plant’s health, appearance, and flowering potential, guiding its growth to become fuller and produce more prolific blooms.
Why Prune Yarrow
Pruning yarrow offers several benefits. Regularly removing spent flowers encourages more blooms throughout the growing season, extending its display of color. This practice also helps maintain a tidy and compact plant shape, preventing yarrow from becoming leggy or floppy, especially in rich soils or humid conditions. Pruning helps control aggressive self-seeding, preventing unwanted spread. Removing damaged or diseased foliage promotes better air circulation, reducing fungal issues like powdery mildew.
When to Prune Yarrow
The timing of yarrow pruning varies by season. A significant cutback in early spring, often called the “Chelsea Chop,” is beneficial before new growth emerges. This encourages a bushier habit and a more compact plant with multiple flowerheads. Mid-season, after the first flush of blooms, deadhead spent flowers to encourage continuous reblooming. This redirects the plant’s energy from seed production to new flower buds, often leading to a second wave of blooms into autumn. A final cutback can be performed in late fall after the last blooms fade, or delayed until early spring. While some gardeners leave spent foliage for winter interest, cutting back in fall can tidy the garden and help prevent disease spread.
How to Prune Yarrow
Use clean, sharp pruning shears or clippers for precise cuts that heal quickly. When deadheading, locate the stem just below the faded flower head. Make a cut above a lateral leaf or bud, which encourages new side shoots and continuous blooms.
For a substantial spring cutback, especially if the plant has become leggy, trim the entire plant back to 4 to 6 inches from the ground, ensuring cuts are made above any new basal growth. In the fall, either cut the plant back hard, similar to the spring cut, or simply remove spent flower stalks and any yellowing or damaged foliage.
When shaping the plant or addressing overly dense growth, lightly trim stems to improve air circulation and maintain an appealing form. Always remove any diseased or dead branches at any time during the growing season to prevent issues from spreading.
After Pruning Care
After pruning, proper care helps yarrow recover and thrive. While established yarrow is drought-tolerant, provide water, especially after a significant cutback, to support new growth. Water deeply but infrequently, allowing the soil to dry between waterings to prevent root rot, as yarrow prefers well-draining conditions.
Yarrow is generally low-maintenance regarding nutrients and typically does not require extensive fertilization. Over-fertilizing can lead to excessive foliage growth at the expense of blooms and may cause the plant to flop. If desired, a light application of a balanced, slow-release fertilizer or a thin layer of compost in early spring can be beneficial. Monitor the plant for new growth and overall health.