Yarrow (Achillea millefolium) is a perennial herb native to temperate regions of the Northern Hemisphere. Known for its feathery foliage and clusters of small, daisy-like flowers, yarrow is highly adaptable to various soil conditions and climates. From a plant's perspective, its resilience and reproductive strategies make it an ideal candidate for supporting pollinators.
Yarrow's flowers are arranged in flat-topped compound inflorescences called corymbs, which provide a stable landing platform for pollinators. Each tiny flower within the cluster produces nectar and pollen, rewarding visitors. The plant's white, yellow, or pink hues and mild fragrance are tailored to attract bees, butterflies, and other insects. Its UV-reflective patterns, invisible to humans but detectable by pollinators, further enhance its visibility.
Yarrow secretes nectar continuously during daylight hours, ensuring a steady food supply for pollinators. Its pollen grains are small and sticky, easily adhering to insect bodies for cross-pollination. As a generalist plant, yarrow does not rely on specific pollinators, increasing its ecological versatility. The prolonged blooming period (early summer to fall) aligns with the active seasons of many pollinators, providing sustained resources.
Yarrow supports a diverse range of pollinators, including honeybees, native bees (e.g., sweat bees and bumblebees), syrphid flies, and beetles. Its open flower structure accommodates both short- and long-tongued insects. By hosting predatory insects like parasitic wasps, yarrow indirectly benefits pollinators by reducing pest populations that might otherwise damage pollinator habitats.
Yarrow's stems are sturdy, preventing collapse under the weight of multiple pollinators. The plant's drought tolerance ensures nectar production even in arid conditions, a critical adaptation for pollinator survival during resource scarcity. Additionally, yarrow's ability to thrive in disturbed soils makes it a pioneer species in degraded habitats, restoring pollinator pathways in fragmented landscapes.
Yarrow and pollinators engage in mutualism: the plant gains efficient pollen transfer, while insects receive nourishment. Butterflies, such as the painted lady (Vanessa cardui), use yarrow as a nectar source during migration. Native bees collect pollen for larval provisioning, inadvertently fertilizing nearby yarrow plants. This interdependence underscores yarrow's role in sustaining pollinator life cycles.
Unlike ornamental plants bred for double flowers (which often lack nectar or accessible reproductive parts), yarrow retains its wild-type simplicity, ensuring pollinator access. Its chemical defenses, such as sesquiterpene lactones, deter herbivores without repelling pollinators—a balance many cultivated plants fail to achieve.
