Achillea borealis, Common Yarrow

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Common Yarrow has ferny faintly medicinal-smelling leaves that grow in a low rhizome-spreading jumbly mat, with upright stalks bearing multiple flat-topped to slightly domed white flower clusters. Reminiscent of Queen Anne’s Lace to those familiar with that plant’s distinctive umbel, but shorter overall and with smaller denser flowers.

Cultivation

Handsome to Invasive

This plant does quite well in poor to average soil, in dry to moist conditions, as long as it has good sun. Because the foliage is rather delicate and loose in overall structure, Yarrow looks best when blended with other wildflowers of similar height where it can offer a pleasing accent of texture and color to a mixed planting. See notes below under Ecology: A Very Confusing Native Status as the native Yarrow seems to become readily overwhelmed by other more vigorous plants, whereas other Yarrow, possibly non-native is reported to be incredibly invasive.

A number of handsome cultivars improve dramatically on the form, introducing colors and sturdier foliage that can be planted as specimens or in masses. Follow the culture notes included with your cultivar when siting these.

Human Uses

Steeped in herbal lore and Old World mythology, Achillea millefolium has an interesting section in Wikipedia on its chemistry.

Ecology

A Very Confusing Native Status

A true consensus on its native status does not exist, however, most agree we have both native and introduced Achillea in North America. The Atlas of the Virginia Flora calls it native to Virginia and to Floyd. According to the USDA, “Introduced and native phases differ primarily in chromosome number and are difficult to distinguish morphologically.” It also tends to hybridize extensively to the point that “all efforts to organize an intraspecific taxonomy on a North American basis” have failed (USDA). The Digital Atlas of the Virginia Flora calls it Achillea millefolium, the name used for the species worldwide, while acknowledging the synonyms Achillea millefolium var. occidentalis and Achillea borealis. As of July 2023, per personal communication, Virginia DCR uses Achillea borealis.

There are a great many anecdotal stories about both Yarrow’s invasive behavior as well as about its polite presence in American wildflower communities, suggesting this same confusion of identity between native and introduced subspecies. Prairie Moon Nursery does not include it in their catalog, citing “its aggressive nature, wide natural presence, and the dubious nativity of specific stands,” though noting that the Xerces Society champions its benefit to insects.

Conservation Biological Control

Like other plants with small flowers, yarrow supports wasps and other insect predators which are vital to keeping an ecosystem strong and balanced. This is also known as “Conservation Biological Control.” Read the Xerces Society’s handbook Habitat Planning for Beneficial Insects as well as Heather Holm’s Pollinators of Native Plants: Attract, Observe and Identify Pollinators and Beneficial Insects with Native Plants.