Plant of the Week: Common Yarrow

This entry is from Lucas Costner, an undergraduate horticulture major at Oregon State University.  It highlights one of the plants that Aaron Anderson is using in his research.

Common Yarrow (Achillea millefolium) isn’t just common — it’s nearly ubiquitous throughout the Pacific Northwest. Found in lawns, along roadsides, in fields and gardens, it’s easy to allow yarrow’s abundance to overshadow its potential in the landscape, its benefit to wildlife, and its historical value as a medicinal plant. 

A perennial native across the temperate Northern Hemisphere, yarrow has a long history of human association (1, 2). Its scientific name, Achillea, comes from the ancient Greek hero Achilles, who used the plant to help dress battle wounds (2). Similarly, in the Northwest, indigenous peoples made poultices and teas from the plant (2). 

In the landscape, it may be helpful for gardeners to consider mimicking natural distribution patterns by massing yarrow into larger groups of plants (3). Yarrow grows densely — emerging up to three feet in height and spreading from a fibrous horizontal root system (1). White, sometimes pink, ray flowers appear at the end of stems in nearly flat inflorescences (2). These plants are very drought tolerant and appear naturally in disturbed areas, meaning they will thrive in the average garden (1). 

As a member of the Asteraceae family along with goldenrod and Douglas aster, yarrow’s bountiful floral display offers excellent forage for generalist pollinator species throughout the summer months and is a common choice for butterfly gardens (1). In addition to its floral resources, the foliage is noted as a source of food and habitat to many species of butterfly and moth caterpillars (4). 

References: 

1. Hurteau, M. D. (2013, November 13). Common Yarrow [PDF]. USDA NRCS National Plant Data Center.

2. Mathews, D. (2016). Natural History of the Pacific Northwest Mountains. Portland, OR: Timber Press.

3. Rainer, T., & West, C. (2015). Planting in a Post Wild World. Portland, OR: Timber Press.

4. Robinson, G. S., P. R. Ackery, I. J. Kitching, G. W. Beccaloni & L. M. Hernández, 2010. HOSTS – A Database of the World’s Lepidopteran Hostplants. Natural History Museum, London. http://www.nhm.ac.uk/hosts. (Accessed: 29 Aug. 2018).