Yarrow (Achillea millefolium) is a garden perennial highly successful at attracting butterflies and other beneficial insects. This common plant is a member of the Asteraceae family, which also includes daisies and sunflowers. Yarrow’s unique structure and accessibility make it a frequent and preferred stop for butterflies searching for nectar. Incorporating this hardy plant into a garden increases its value to the local ecosystem.
Physical Features That Attract Butterflies
Yarrow’s appeal begins with the architecture of its bloom, composed of many tiny flowers grouped into a flat-topped cluster called a corymb. This composite structure creates a broad, stable landing platform for butterflies, allowing them a secure place to rest while feeding. Yarrow’s shallow florets make the nectar easily accessible to many different species, unlike deep, tubular flowers that require specialized long tongues. The nectar is readily available even to butterflies with shorter proboscises, such as Checkerspots, Hairstreaks, and American Ladies. The flower head, typically two to four inches wide, offers a rich, concentrated source of energy.
Selecting and Siting Yarrow for Pollinators
For maximum butterfly attraction, gardeners should prioritize the native species, Achillea millefolium, over highly hybridized ornamental cultivars. Native varieties tend to have more accessible nectar and pollen compared to hybrids bred for color or bloom size. Although colorful cultivars are visually appealing, they may receive less frequent butterfly visits.
Yarrow thrives best when planted in full sun, ideally six or more hours of direct sunlight daily, which is also the preferred environment for most butterfly activity. Full sun exposure promotes the strongest, most compact growth habit for the plant. The soil should be well-drained and relatively lean, as yarrow naturally grows well in poor or average conditions.
Avoid rich soil and excessive nitrogen-heavy fertilizer, as this encourages the plant to grow too tall and spindly. Over-fertilization causes the plant to produce weak, floppy stems and leaves instead of sturdy, high-quality blooms. A light application of compost or a low-nitrogen fertilizer in the spring is usually sufficient to support healthy growth and prolific flowering.
Yarrow’s Function Beyond Nectar Provision
Beyond serving as a nectar source for adult butterflies, yarrow supports the garden ecosystem in other ways. The native Achillea millefolium is a documented larval host plant for the Painted Lady butterfly (Vanessa cardui). This means the plant’s foliage is a necessary food source for the caterpillar stage of this butterfly species.
Yarrow is valuable for its ability to attract a range of beneficial predatory insects that assist with natural pest control. Its shallow, composite flowers provide nectar and pollen for small parasitoid wasps, which cannot access nectar in deeper blooms. These non-stinging wasps lay their eggs inside garden pests, helping to keep damaging caterpillar and beetle populations in check.
The plant also attracts other beneficial predators, including lady beetles, minute pirate bugs, and hoverflies. Adult hoverflies feed on the accessible pollen and nectar, while their larvae consume soft-bodied insects like aphids. By supporting this diverse community of beneficial insects, yarrow contributes to the overall health and balance of a garden.