E-Flora BC: Electronic Atlas of the Flora of British Columbia

Achillea millefolium L.
yarrow (common yarrow)
Asteraceae (Aster family)

Introduction to Vascular Plants

© Ashley Churchill  Email the photographer   (Photo ID #29926)

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Distribution of Achillea millefolium
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Species Information

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General:
Perennial, aromatic herb, usually rhizomatous; stems erect, slender, 10-100 cm tall.
Leaves:
Fernlike, alternate, stalked below and unstalked above, pinnately dissected, the divisions again dissected.
Flowers:
Heads numerous, in a short, flat or round-topped cluster; involucral bracts dry, overlapping in several series, often dark-margined; ray flowers usually 3-8, 2-3.5 mm long, white to sometimes pink or reddish; disk flowers 15-40, cream colored.
Fruits:
Achenes glabrous, flattened, 1-2 mm long; pappus lacking.
Notes:
Taxonomically, one of our most complex species. Tyrl (1980) presented a sound case for recognizing only a single variable species. I, however, have recognized four, broad ecogeographical forms (sensu Nobs 1960) at the varietal level since these forms are ecologically significant in BC.

1. Leaves grey, long-hairy to woolly; plants usually in and east of the Coast-Cascade Mountains.

2. Involucral bract margins light brown to black; stems usually less than 30 cm tall; plants of the subalpine and alpine zones................. var. alpicola (Rydb.) Garrett

2. Involucral bract margins light brown to straw-coloured; stems usually more than 30 cm tall; plants of the montane and steppe zones........................ var. lanulosa (Nutt.) Piper in Piper & Beattie

1. Leaves usually green, moderately long-hairy; plants of coastal regions.

3. Involucral bract margins dark brown to black; stems 10-40 cm tall........................ var. borealis (Bong.) Farwell

3. Involucral bract margins hyaline to light straw-coloured; stems 30-100 cm tall.................. var. pacifica (Rydb.) G.N. Jones

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
White
Blooming Period:
Early Summer
Fruit/Seed characteristics:
Colour: Brown
Present over the Summer
Source:  The USDA

Habitat / Range

Mesic to dry coastal bluffs, meadows, grasslands, rocky slopes and open forests in all vegetation zones; common throughout BC; N to AK, YT and NT, E to NF and S to FL, TX, CA, and MX. Description

Source: The Illustrated Flora of British Columbia

Additional Notes

This species has been observed flowering in the Fraser Delta in December.

Ecology

Ecological Framework for Achillea millefolium

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class

Minimum

Average

Maximum

Elevation (metres) 0 1143 2854
Slope Gradient (%) 0 24 360
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
0 189 360
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 3 8
Modal Nutrient Regime
Class
C
Number of field plots
 species was recorded in:
8643
Modal BEC Zone Class
IDF
All BEC Zones (# of stations/zone) species was recorded in: AT(124), BAFA(34), BG(471), BWBS(468), CDF(63), CMA(4), CWH(110), ESSF(1352), ICH(346), IDF(2274), IMA(24), MH(18), MS(822), PP(577), SBPS(448), SBS(848), SWB(178)

Climate

The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Achillea magna auct.

Taxonomic and Nomenclatural Links

Additional Photo Sources

Related Databases

General References