Milfoil, Common Yarrow
- Eudicots are a major lineage of flowering plants; see family for general characteristics
- Sunflower Family (Asteraceae)
- Herbaceous perennial
- Alternate (1 leaf at each junction with stem) and compound (divided into leaflets)
- Fern-like, with varying degrees of hairiness
- Inflorescence (flower arrangement) is a branching, flattened dome of many composite flowerheads
- Each radiate flowerhead (see Sunflower family) has
- 3-8 outer white 3-lobed ray flowers, suggesting petals
- 15-40 central white disk flowers, with orange stamens (male flower parts)
- Phyllaries (vase-like floral bracts, collectively called the involucre) in 3-4 rows
- Ovary inferior (below the attachment of other flower parts)
- Fruit is an achene (a single-seeded, dry fruit that does not split open)
- Height 8-16 in.
- Native to California
- Grows in woodlands, forests, and grasslands, especially in disturbed areas
- See Calflora for statewide observations of this plant
- Circumboreal, occurring throughout the Northern Hemisphere
- Grows at elevations to 12,000 ft.
Uses (San Mateo County Parks prohibits removal of any natural material)
- Some cavity-nesting birds, e.g., European starlings, use leaves to line their nests
- Food source for many insects, including bees and butterflies, like the Lorquin admiral (Limenitis lorquini), west coast lady (Vanessa annabella), western brown elfin (Incisalia augustinus iroides), and gray hairstreak (Strymon melinus) butterflies
- Long history of medicinal use because of its astringent effects
- One of the medicinal herbs found at a 60,000-year-old Neanderthal burial site in Iraq
- Many of its common names, like woundwort, bloodwort, stanchwort, carpenter’s weed, sanguinary, herba militaris, and nosebleed, suggest its use to stanch the flow of blood
- Native people used yarrow for a variety of ailments, including fever, toothaches, earaches, general pain relief, and burns
- CAUTION – Yarrow is toxic to dogs, cats, and horses (ASPCA 2022)
- Achillea (ak-ILL-ee-a) – named for the Greek hero Achilles: according to Greek mythology, Achilles used yarrow to treat the wounds of his soldiers
- millefolium (mil-eh-FO-lee-um) – from the Latin for “thousand leaves,” referring to the finely dissected leaves
- Yarrow – from the Old English gearwe, of uncertain origin; cognate of Old High German garwa and Dutch gerwe
- Flowers at Edgewood are white, but yarrow comes in shades of pink as well!
- Jepson notes that yarrow is highly variable, especially in leaf size and hairiness
- May become weedy or invasive in some regions or habitats (Winslow 2006)
- May be confused with golden-yarrow (Eriophyllum confertiflorum var. confertiflorum), also in the Sunflower family, and with yampah (Perideridia kelloggii) in the Carrot family
|Growth Habit||herbaceous perennial||small evergreen shrub||herbaceous perennial|
|Leaves||finely-cut, fernlike leaflets||deeply-lobed, silver grey to woolly||narrow, blade-like leaflets (wither before flowers appear)|
|Inflorescence||flattened dome of flowerheads||dense clusters of flowerheads||double umbel¹ of uncrowded flowerheads|
|Flower Color||white to pink||golden yellow||white|
- Found in serpentine and non-serpentine grasslands and open woodlands
- See iNaturalist for observations of this plant
- Flowers April – July
American Society for the Prevention of Cruelty to Animals (ASPCA) 2022. Yarrow.
Shapiro, A.M. and Manolis, T.D. 2007. Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions. University of California Press, Berkeley – Los Angeles, California.
Winslow, S.R. 2006. Plant fact sheet: Western yarrow (Achillea millefolium L. var. occidentalis DC.). U.S. Department of Agriculture, Natural Resources Conservation Service, National Plant Data Center. Plant Materials Center. Bridger, Montana.