Achillea, commonly called yarrow, is a sturdy, carefree, and steady bloomer from summer through fall in Sonoma County’s Mediterranean climate. It is a genus of approximately 85 perennial species, one of which will fit into nearly any garden style: wildflower to rock garden, cottage garden or herbaceous border.
Common yarrow most often found in nurseries and popular in gardens has gray-to-green, usually finely divided, aromatic leaves that appear feathery or fern-like. The flower is a flat cluster of many daisy-like flower heads frequently white or yellow, but new cultivars and hybrids offer a wide range of colors from pink to red to lavender.
Some species originating from mountainous regions are low-growing mounds or mats. Others, originating from grasslands, develop taller stems. They tolerate many different soil types and conditions, but do require moderate to occasional water until established when they become drought tolerant. All grow best in full sun and fast-draining soil.
Care for achillea is simple and straightforward. Remove spent flowers and trim back occasionally. To maintain their vigor, divide when they become crowded. Problems with this ornamental are few, but aphids, rust, and other fungal diseases can occur; however, if planted in the right spot and given the simple care they need, problems are rare. For some gardeners, contact with foliage may aggravate skin allergies.
Butterflies, bees, beneficial predatory insects, and parasitic wasps are all attracted to achillea’s corymbs (flattened flower heads), making it an important habitat plant. Taller varieties are also valued as cut flowers added to fresh or dried arrangements.
For white cultivars, try short-stemmed Achillea agerafolia or taller A. millefolium. (Be warned, however, A. millefolium, or common yarrow, can spread rapidly and become invasive.)
For yellow achillea, plant A. clypeolata or A. filipendulina ‘Coronation Gold’ or ‘Gold Plate’ among others.
For tones of pink, select light pink Achillea ‘Forncett Candy’ or A. millefolium ‘Cerise Queen’ or ‘Island Pink’, both darker pink.
Red is found in A. ‘Fanal’ that fades with age.
Achillea ‘Terra Cotta’ or A. ‘Paprika’ have more earth-toned flowers. For something really interesting, select A. ‘Summer Pastels,’ whose blossoms combine lavender, purple, white, apricot, cream, rose, and pink.