Yarrow, scientifically named Achillea millefolium, belongs to the Achillea genus within the Asteraceae family, commonly known as the aster, daisy, or sunflower family. The species name “millefolium” means “thousand-leaved,” referring to the finely divided, feathery leaves of the plant. This perennial herb is known for its flat-topped or slightly domed clusters of small flowers.
Achillea millefolium is native to regions across the Northern Hemisphere, including Europe, Asia, and North America. In North America, it’s widespread, naturally occurring from Alaska down through Canada and into the United States, where it’s found in every state except Hawaii. It thrives in a variety of habitats, from meadows and grasslands to roadsides and disturbed areas, showing its adaptability to different soil types and conditions.
Yarrow has a rich historical background, with evidence of its use dating back thousands of years. Named after Achilles, the Greek hero of the Trojan War, who supposedly used it to heal wounds, Yarrow has been cherished for its medicinal properties across various cultures. Ancient Greeks and Romans used it for treating wounds, reducing inflammation, and stopping bleeding. In Native American cultures, it was used for similar medicinal purposes, and its leaves were also employed for pain relief, fever reduction, and as a digestive aid. Over time, Yarrow has also found its place in folklore, often associated with love and healing, and in gardening, valued for its ornamental appeal, attracting butterflies and bees.
Yarrow is hardy in USDA Hardiness Zones 3 through 9, reflecting its wide adaptability to different climates. This range allows it to grow in areas with cold winters and hot summers, demonstrating its resilience to both frost and drought. It prefers full sun but can tolerate some shade, making it suitable for a variety of garden settings, from wildflower meadows to formal gardens, where it’s appreciated for its long bloom period, easy care, and ability to thrive in poor soil conditions. Its versatility in landscaping, combined with its historical and ecological significance, makes Yarrow a favored plant among gardeners and naturalists alike.
The range of Achillea millefolium, known as Yarrow, is remarkably extensive, covering much of the Northern Hemisphere. It is native to Europe, Asia, and North America, where in the latter it grows from Alaska through Canada and into all states of the U.S. except for Hawaii. This species adapts to a broad spectrum of environments, from natural habitats like meadows and grasslands to human-altered landscapes such as roadsides, demonstrating its versatility and widespread presence across diverse ecological niches.
Yarrow (Achillea millefolium): Identifying Characteristics
- Yarrow typically grows to a height of 1 to 3 feet, with some varieties reaching up to 4 feet. It can spread 1 to 3 feet wide, forming dense clumps or spreading through rhizomes in favorable conditions.
- The leaves are finely divided, giving them a fern-like or feathery appearance. They are alternate, lance-shaped overall but pinnately dissected into numerous small segments, hence the species name “millefolium.” Leaves are usually 2 to 5 inches long, with smaller leaflets that are linear to lanceolate. They are typically green but can appear grayish-green due to a layer of fine hairs, especially on the underside.
- Yarrow is known for its moderate to fast growth rate once established. It can spread quickly through both seeds and underground rhizomes, making it somewhat aggressive in garden settings if not managed.
- The root system of Yarrow includes both a taproot and spreading rhizomes. The taproot anchors the plant deeply into the soil, providing drought resistance, while the rhizomes allow it to spread and colonize new areas, sometimes leading to it being considered invasive in certain contexts.
- As a perennial, Yarrow can live for several years under good conditions, with individual plants often returning year after year. However, in the wild, the lifespan can vary due to environmental factors, competition, and human activities.
- Yarrow produces flat-topped or slightly domed clusters of small flowers, forming an inflorescence known as a corymb. Typically white, but cultivars can offer a range of colors including pink, red, yellow, and various shades of purple. Flowers from late spring to early fall, offering a long blooming period that’s attractive to pollinators.
- Yarrow has a distinctive, somewhat spicy or medicinal scent when the leaves are crushed, which is often used as an identifying characteristic in the field.
- It’s adaptable to a variety of soil types, from sandy to clay, preferring well-drained conditions but tolerating poor soil. It thrives in full sun but can handle some shade, showing resilience in both drought and moderately wet conditions.
- Stems are erect, often woody at the base, and can be slightly hairy. Yarrow supports pollinators like bees, butterflies, and beneficial insects, contributing to garden biodiversity.
Yarrow (Achillea millefolium): Cultivation
Site Selection
Choose a location with full sun for best flowering, though Yarrow can tolerate light shade. It’s adaptable to various soil types but prefers well-drained, not overly fertile soils. Yarrow can thrive in dry, sandy, or rocky soils where many plants might struggle, making it excellent for xeriscaping or low-maintenance gardens.
Planting
- Timing: Plant in spring after the last frost or in early fall. If starting from seeds, sow them directly in the garden in late fall or early spring for natural stratification.
- Spacing: Space plants or seeds about 1 to 2 feet apart to allow for growth and air circulation, as Yarrow can spread.
- Process: Dig a hole similar in depth to the root ball for transplants. If from seed, lightly cover with soil. For divisions or transplants, ensure the root system is well spread out or slightly teased apart before placing in the hole.
Watering
- Water newly planted Yarrow regularly until established, which might take the first growing season. Once established, it’s quite drought-tolerant, requiring little supplemental watering except in extreme heat or prolonged dry spells. Overwatering can lead to root rot, so ensure good drainage.
Mulching
- A thin layer of mulch can help retain soil moisture and reduce weed competition, but too much mulch can retain too much moisture around the crown, potentially causing rot. Keep mulch away from the base of the plant.
Fertilization
- Yarrow generally doesn’t require much fertilization, as it can thrive in nutrient-poor soils. If the soil is very poor, a light application of balanced or slow-release fertilizer in spring can encourage growth, but avoid over-fertilizing, which can lead to weak, leggy growth.
Pruning and Maintenance
- Deadheading: Remove spent flowers to encourage further blooming and to prevent self-seeding where you don’t want it to spread.
- Cutting Back: After the first bloom, you can cut back the plant by about one-third to promote a second flush of flowers.
- Winter Care: In colder zones, a light mulch around the plant can protect the root system, though Yarrow is quite hardy.
Propagation
- Seeds: Sow seeds in situ or start them indoors 6-8 weeks before the last frost for transplanting.
- Division: Divide established clumps every few years in spring or fall to rejuvenate the plant and control spread.
- Cuttings: Softwood cuttings can be taken in late spring or early summer.
Pest and Disease Management
- Generally resistant to pests and diseases, Yarrow might occasionally face issues like aphids or powdery mildew. Manage with water sprays for aphids or improve air circulation to prevent mildew. If problems persist, consider organic treatments.
Control of Spread
- Yarrow can become aggressive through its rhizomes and seeds. If you need to control its spread, consider using barriers for the roots or deadhead regularly to prevent seeding.
Harvesting for Use
- Leaves and flowers can be harvested for medicinal or culinary uses throughout the growing season. Harvest in the morning after the dew has dried for the highest concentration of essential oils.