Kingdom: Plantae

Phylum: Magnoliophyta -- flowering plants

Class: Magnoliopsida -- dicots

Family: Asteraceae (Compositae) -- sunflower

Common Name: yarrow

Species Code: ACMI2

Origin: Achillea is a circumboreal species widespread in Europe and North America. It has a broad ecological amplitude and is widely adapted to sites with full sun. It seems to prefer some disturbance.

Rare: no

Form: forb; aromatic, rhizomatous

Duration: perennial

Longevity: short-lived

Habitat Type: prairie, forest, shrub thickets.

Wetland Indicator Status: FACU

Leaves: Alternate, slender, finely pinnately dissected, basal leaves petiolate, cauline leaves without petioles

Mature height: 4-38 inches

Flowers: White (sometimes pink?), numerous in a flat-topped inflorescence; April-Oct.
Disc flowers are perfect, ray flowers pistillate.

Flower color: white

Bloom: April, May, June, July, sometimes extending into August, September, October

Fruit: achene, compressed, 2mm long.

Characteristics:
Achillea is a polyploid complex with wide variability and many varieties and/or subspecies have been proposed. Other treatments lump them all as synonyms of A. millefolium.
The common western native phase, sometimes called var. occidentalis, is usually a tetraploid. Other native subspecies or varieties of more restricted geographical occurrence may be hexaploids, as is the European A. millefolium var. millefolium.
The native forms have the leaves highly dissected, with the leaf segments more numerous and in multiple planes, so that the leaf appears thick. They are also more pubescent, appearing grey-green rather than green (Hitchcock et al 1969).
Tyrl (1975) found both tetraploids and hexaploids in native populations. He concluded hexaploids originated thru autoploidy from tetraploids. They are not isolated geographically or by compatibility.
2,835,000 seeds/lb (USDA NRCS Pullman PMC 2005).
2,700,000-4,125,000 seeds/lb (Hassell et al 1996).
3,411,818 seeds/lb (USDA NRCS PLANTS Database 2006).
2,770,000 seeds/lb (Kingery et al 2003).
x=9, 2n=36.
Insects are the primary pollinators (Warwick & Black 1982).
Apomixis is known to occur in the genus.
Plants are self-incompatible and always outcrossed (Warwick & Black 1982).
Has many medicinal uses. May be toxic.
Sheep eat the plants (St. John 1963). Plants are of minor value to Rocky Mountain elk in summer, winter and fall (Kufeld 1973). Has little forage value for cattle and fair value for sheep and deer (Roche & Roche 1991). Livestock do not use the plants if other forage is available. Small rodents, rabbits, and grouse make minor use of the plants (Sedivec & Barker 1998). The plants are an important food for deer in autumn and are used by a wide variety of insects (Warwick & Black 1982). May contain toxic compounds (Stubbendieck et al 1997).
Plants are short-lived but reproduce readily from seed. They also spread by rhizomes but not as vigorously as some of the introduced horticultural yarrows.

Comments: Achillea millefolium var. lanulosa in St. John 1963, and in Piper & Beattie 1914.
Achillea lanulosa and A. millefolium var. or ssp. lanulosa are synonymous.

Sun requirement: full to partial

Soil moisture: xeric to mesic

Precipitation: 8-26 inches (USDA NRCS PLANTS Database 2009)

Fire: Survives most fires, increases rapidly from both rhizomes and seeds (Aleksoff 1999). Moderately resistant, regenerating from seeds to preburn levels within 5-10 years (Patterson et al 1985).
Forest populations are susceptible to fire because the rhizomes grow in the duff layer (McLean 1969).

Hazards: May contain toxic compounds (Stubbendieck et al 1997). Allergens in the plants may cause skin irritations (Warwick & Black 1982).

Sowing time: spring

Transplant time: spring

Stratification: none

Seed yield: high

Seed harvest: medium difficulty

Seed first harvest: first year

Seed cleaning: easy

Planting duration: short

Seed insect problem: none noted

Seed shatter: low

Seed size: very small

Seed harvest date: early Sept

Seed comments: Large-scale growers report that the dust is highly flammable and harvest equipment must be kept free of dust.

Propagation:
9 protocols in the Native Plant Network

Other propagation information:
Untreated seed has high germination (Sorenson & Holden 1974).
Peak germination in fall, no stratification required (Baskin & Baskin 1988).
Alpine seed needs 1 month after-ripening (Kaye 1997).
Best germination at 22/17^oC day/night (McDonough 1970).
Best germination at 15/25^oC night/day (Robocker 1977).
Highest germination at 17/12^oC, but higher temps also gave very high germ rates (McDonough 1969).
Buried rhizome fragments containing at least 1 node regenerate from the soil. Deeper burial results in lower emergence. Surface fragments do not survive (Bourdot 1984).
Highest germination in the dark at 20/30^oC (Maguire & Overland 1959).

References:
Aleksoff, Keith C. 1999. Achillea millefolium. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2009, July 12].

Baskin, Carol C., and Jerry M. Baskin. 1988. Germination Ecophysiology of Herbaceous Plant Species in a Temperate Region. Am. J. Bot. 75:286-305.

Bourdot, G.W. 1984. Regeneration of Yarrow (Achillea millefolium L.) Rhizome Fragments of Different Length from Various Depths in the Soil. Weed Research 24:421-429.

Hassell, Wendell, W. Rocky Beavers, Steve Ouellette, and Thomas Mitchell. 1996. Seeding Rate Statistics for Native and Introduced Species. US Dept of Interior and USDA, NRCS. Denver, CO.

Kaye, T.N. 1997. Seed Dormancy in High Elevation Plants: Implications for Ecology and Restoration. In, Kaye, T.N., A. Liston, R.M. Love, D. Luoma, R.J. Meinke, and M.V. Wilson [editors]. Conservation and Management of Native Plants and Fungi. Native Plant Society of Oregon, Corvallis, Oregon.

Kingery, James, Angela Cotter, and Kendra Moseley. 2003. Idaho Roadside Revegetation Handbook. Prepared for: Idaho Transportation Department. Department of Rangeland Ecology and Management, University of Idaho. Online at http://h237-41.state.id.us/highways/ops/maintenance/Manuals/fullVegetationManual.pdf

Kufeld, Roland. 1973. Foods Eaten by the Rocky Mountain Elk. Journal of Range Management 26:106-113.

Maguire, James D. and Alvin Overland. 1959. Laboratory Germination of Seeds of Weedy and Native Plants. Washington State Agricultural Experiment Station Circular 349, Pullman, WA. 15 p.

McDonough, Walter T. 1969. Effective Treatments for the Induction of Germination in Mountain Rangeland Species. Northwest Science 43:18-22.

McDonough, Walter T. 1970. Germination of 21 Species Collected from a High Elevation Rangeland in Utah. American Midland Naturalist 84:551-554.

McLean, Alastair. 1967. Germination of Forest Range Species from British Columbia. Journal of Range Management. 20:321-322.

Patterson, Patricia A, Kenneth E. Neiman, and Jonalea R. Tonn. 1985. Field Guide to Forest Plants of Northern Idaho. USDA Forest Service Intermountain Research Station. General Technical Report INT-180. Ogden, Utah.

Robocker, W.C. 1977. Germination of Seeds of Common Yarrow (Achillea millefolium) and its Herbicidal Control. Weed Science 25:456-459.

Roche, Ben F., Jr. and Cindy Talbott Roche. 1991. Eastern Washington Range Plants. Extension Bulletin 1302, Washington State University Coop. Extension Service, Pullman WA. 66 pp.

Sedivec, Kevin K., and William T. Barker. 1998. Selected North Dakota and Minnesota Range Plants. North Dakota State University Department of Animal and Range Sciences Extension Bulletin EB-69. Fargo, North Dakota. Online at http://www.ag.ndsu.edu/pubs/ansci/range/eb69-2.htm Accessed 12/10/06.

Sorensen, J.T. and D.J. Holden. 1974. Germination of Native Prairie Forb Seeds. Journal of Range Management 27:123-126.

St. John, Harold. 1963. Flora of Southeastern Washington and of Adjacent Idaho. 3rd edition. Outdoor Pictures. Escondido, CA.

Stubbendieck, James, Stephan L. Hatch, and Charles H. Butterfield. 1997. North American Range Plants. 5th edition. University of Nebraska Press, Lincoln, NE. 501 pp.

USDA, NRCS, Pullman Plant Materials Center. 2005. Seed Weights of Some Palouse Native Species. Pullman Plant Materials Center, Pullman, Washington. Online at http://www.wsu.edu/~pmc_nrcs/Docs/Seed_Weights_Palouse_Native_Species.pdf

USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov, 13 July 2009). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Warwick, S.I. and L. Black. 1982. The Biology of Canadian Weeds; 52. Achillea millefolium L. s.l. Canadian Journal of Plant Science 62:163-182.

Links:
Plant Profile from the USDA PLANTS Database
Species account from the Fire Effects Information System
Species description from Flora of North America
Species information from the University of Washington Herbarium