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| ## western yarrow {#western-yarrow .Title-Header}                     |
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| *Achillea millefolium* L. var. *occidentalis* DC.                     |
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| Plant Symbol = ACMIO                                                  |
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Contributed by: USDA NRCS Bridger (MT) Plant Materials Center

![](media/image2.jpeg){width="2.907638888888889in" height="2.175in"}

##### Alternate Names {#alternate-names .Header-3}

##### Woolly yarrow; *Achillea millefolium* L. ssp. *occidentalis* (DC.) Hyl, *Achillea millefolium* L. var. *lanulosa* (Nutt.) Piper; *Achillea millefolium* L. ssp. *lanulosa* (Nutt.) Piper {#woolly-yarrow-achillea-millefolium-l.-ssp.-occidentalis-dc.-hyl-achillea-millefolium-l.-var.-lanulosa-nutt.-piper-achillea-millefolium-l.-ssp.-lanulosa-nutt.-piper .Header-3}

##### Uses {#uses .Header-3}

*Conservation:* Western yarrow is an early successional species that
readily establishes on disturbed sites. It is recommended for adding
species diversity in native seed mixtures for rehabilitation of
disturbed sites such as rangelands, mined lands, roadsides, park and
restoration areas, prairie reconstruction projects, and farm bill
program conservation plantings. Secondary use is for ornamental
application in pollinator friendly, low maintenance, or naturalized
landscapes.

*Forage:* Western yarrow is a food source for bighorn sheep, pronghorn
antelope, and deer. Sage-grouse, especially chicks, and other upland
birds rely heavily on the foliage of western yarrow as a food source.
Sage-grouse chicks also benefit from eating the insects associated with
yarrow. In Montana, domestic sheep and goats derive approximately 40
percent of their summer diet from western yarrow, while it constitutes
20 percent of cattle and horse diets (Reitz and Morris, 1939). The
leaves and flowers contain volatile oils, alkaloids, and glycosides that
are considered toxic, but the plant is seldom overgrazed and eaten in
large enough quantities to be harmful to foraging animals.

##### *Ethnobotanic:* Native Americans used western yarrow for many purposes, such as a tea to cure stomach ailments, a poultice on infected wounds, and as a mosquito repellant.  {#ethnobotanic-native-americans-used-western-yarrow-for-many-purposes-such-as-a-tea-to-cure-stomach-ailments-a-poultice-on-infected-wounds-and-as-a-mosquito-repellant. .Header-3}

#####  {#section .Header-3}

##### Status {#status .Header-3}

Please consult the PLANTS Web site and your State Department of Natural
Resources for this plant's current status (e.g., threatened or
endangered species, state noxious status, and wetland indicator values).

##### Weediness {#weediness .Header-3}

Western yarrow is not to be confused with the introduced, invasive
plant, common yarrow (*Achillea millefolium* var. *millefolium*). Common
yarrow has origins in central Asia, the European continent, and the
islands of Scandinavia. It is considerably different from western yarrow
in that it has a much taller stature, aggressive vigor, and weedy
characteristics. Common yarrow also initiates a later sequence of
flowering and seed ripening (Callan, 2002).

Western yarrow is a common component of western rangelands and only
under definite conditions of overgrazing and disturbance could it become
locally abundant (USDA FS, 1937). Yarrow is seldom regarded as a problem
weed (Whitson et al., 1991) except on heavily disturbed, arable sites
with favorable environmental conditions (Kannangara and Field, 1985).

##### Description {#description .Header-3}

*General*: Western yarrow is a member of the Asteraceae (Sunflower)
family that is commonly found in natural and disturbed habitats
throughout the western U.S. (Hitchcock and Cronquist, 1973). It is a
self-incompatible, insect-pollinated species (Clausen et al., 1958)
occurring as native forms that may differ in chromosome number (n=18 or
n=27); native races originating in the western U.S. (except the Pacific
coast) are mostly tetraploid and introduced races mostly hexaploid
(Hitchcock et al 1955). Botanists currently acknowledge genetic and
ecological differentiation among native ecotypes at the local and
regional level (Lavin, 2002; Lesica, 2001).

*Taxonomic*: Western yarrow is a moderately rhizomatous, long-lived,
native, herbaceous perennial forb. It is 30-100 cm tall with few to many
unbranched, erect, lanate stems (Cronquist et al., 2002). Leaves are
alternate, sessile, pinnately dissected, semi-evergreen, and aromatic
with an anthemideous scent (chamomile or dog fennel-like odor). The
basal rosette foliage is up to 25 cm long, and cauline leaves are
typically up to 10 cm long and 3 cm broad. Inflorescences are arranged
in a compound, flat-topped corymb 6-20 cm wide, consisting of numerous,
small flower heads 4-6 mm in diameter. Involucre bracts are usually
pubescent and greenish, with papery, straw-colored margins (Robinson and
Fernald, 1908). Outside ray flower numbers are 3-12, mostly white to
cream-colored, 1-2.5 mm long and encircle the center disk flowers. The
disk flowers number 10-75 each, and are yellow, tubular, perfect, and
seed-producing. Fruit is a flattened, glabrous achene with compressed
margins in a mostly reverse egg-shape with no pappus (USDA FS, 1966).

**Distribution**

For current distribution, please consult the Plant Profile page for this
species on the PLANTS Website.

##### Habitat  {#habitat .Header-3}

##### **Western yarrow is one of the most abundant and widely distributed wildflowers in the western United States. It is circumboreal and grows in a variety of plant communities from Alaska across Canada and into northern Mexico (Johnson and Larson, 1999). Western yarrow prefers full sun on roadsides, hills, canyons, pastures, and disturbed areas. It is scattered in sagebrush areas, open timber, and subalpine zones.**  {#western-yarrow-is-one-of-the-most-abundant-and-widely-distributed-wildflowers-in-the-western-united-states.-it-is-circumboreal-and-grows-in-a-variety-of-plant-communities-from-alaska-across-canada-and-into-northern-mexico-johnson-and-larson-1999.-western-yarrow-prefers-full-sun-on-roadsides-hills-canyons-pastures-and-disturbed-areas.-it-is-scattered-in-sagebrush-areas-open-timber-and-subalpine-zones. .Header-3}

#####  {#section-1 .Header-3}

##### **Western yarrow thrives in droughty conditions on gravelly loam and on thin or sandy soils. It is a common component of such ecological sites as shallow, silty, shallow to gravel, and silty steep (USDA SCS, 1976).** Associated species include western wheatgrass (*Pascopyrum smithii*), bluebunch wheatgrass (*Pseudoroegneria spicata*), prairie Junegrass (*Koeleria macrantha*), Sandberg bluegrass (*Poa secunda*), common gaillardia (*Gaillardia aristata*), big sagebrush (*Artemisia tridentata*), and prairie coneflower (*Ratibida columnifera*).  {#western-yarrow-thrives-in-droughty-conditions-on-gravelly-loam-and-on-thin-or-sandy-soils.-it-is-a-common-component-of-such-ecological-sites-as-shallow-silty-shallow-to-gravel-and-silty-steep-usda-scs-1976.-associated-species-include-western-wheatgrass-pascopyrum-smithii-bluebunch-wheatgrass-pseudoroegneria-spicata-prairie-junegrass-koeleria-macrantha-sandberg-bluegrass-poa-secunda-common-gaillardia-gaillardia-aristata-big-sagebrush-artemisia-tridentata-and-prairie-coneflower-ratibida-columnifera. .Header-3}

##### Adaptation {#adaptation .Header-3}

##### **Western yarrow is highly variable and displays wide ecological amplitude to diurnal temperature, altitude, latitude, and climatic (**Hiesey and Nobs, 1970) **and edaphic conditions (Higgins and Mack, 1987). It is considered an "environmental specialist" due to the successful evolution of a number of ecotypic races (Taylor, 1992).**  {#western-yarrow-is-highly-variable-and-displays-wide-ecological-amplitude-to-diurnal-temperature-altitude-latitude-and-climatic-hiesey-and-nobs-1970-and-edaphic-conditions-higgins-and-mack-1987.-it-is-considered-an-environmental-specialist-due-to-the-successful-evolution-of-a-number-of-ecotypic-races-taylor-1992. .Header-3}

**Establishment**

*Natural:* Western yarrow initiates growth in early spring and blooms
for an extended period of time from late spring through mid summer (Budd
and Campbell, 1959). It reproduces by seed and vegetatively, but in
undisturbed habitats the rhizomes remain attached to the parent plant
and vegetative spread is relatively low (Bostock and Benton, 1979). In
disturbed areas, rhizome fragments do not survive on the soil surface,
and bud sprouting success in buried rhizomes is dependant on fragment
length and soil depth (Bourdot, 1984).

The growth performance of western yarrow is reduced under conditions of
increased competition and shading (Bourdot et al., 1984 and 1985). It is
rated as good in maintaining a state of evergreenness (Monsen et al.,
2004) and is not highly flammable, although flames can wick up through
the hollow, dry flower stalks. Late-spring burning will reduce western
yarrow (Anderson et al., 1970), as will heavy fires. In certain
environments yarrow populations tend to temporarily increase after less
intense fires (Bartos and Mueggler, 1981). Studies conducted on the use
of yarrow as a sodding technique in erosion control projects have
produced satisfactory results (Airhart, 1988).

*Direct Seeding:* Viability of fresh western yarrow seed is generally
high and seeds germinate under normal test conditions in 2 to 8 days,
with 75 percent germination occurring in 5 days (Sorenson and Holden,
1974). Seed should be planted into a firm, weed-free seedbed with a
drill that will ensure uniform seed placement to a depth of ⅛ to ¼ inch
(3 to 6 mm) or broadcast seeded, then harrowed or raked, and firmed with
a packer or roller. Field conditions during seedling emergence must be
monitored for impermeable crusts, especially on sites with clayey soils.
If crusting is observed, the soil crust can be fractured with a roller
or periodic sprinkler irrigation.

There are approximately 4.4 million seeds/lb (9.5 million seeds/kg). The
full seeding rate is ¼ to ½ lb/acre (0.3 to 0.6 kg/ha) pure-live-seed
(PLS), but western yarrow would seldom be seeded in a pure stand. It is
recommended that western yarrow be included as a component of a native
seed mixture, where the seeding rate is adjusted to the desired
potential of the plant community. Spring seeding is preferred over a
dormant fall planting date. Periodic mowing during the establishment
year is one option for weed suppression.

*Containers:* Containers should be sown in fall for outside nursery
production and in spring for production in the greenhouse. Pots are
filled with a well-drained soilless medium and wetted prior to seeding.
Seeds are placed directly on the surface and lightly covered with a thin
layer of the medium, perlite, or pea gravel, and then thoroughly
irrigated. Containers are kept moist with light irrigation or misting
during the establishment phase. Germination occurs in 6 to 14 days at
approximately 70° F, followed by rapid root and shoot development over
the next 60 days. Supplemental nutrition is not necessary, but may be
applied at the recommended rate as a controlled release, encapsulated
fertilizer (Luna et al., 2004).

Potted material should be acclimated to natural spring temperatures for
at least 1 month prior to lining out. The site should be prepared so
that the soil is workable, but not so loose as to resist packing.
Transplants are placed in a hole slightly deeper than the length of the
root ball, firmly tamped to remove unwanted airspace, and watered until
the soil is settled. Additional soil may be required to fill cracks as
they occur around the plants. Supplemental irrigation is advised for as
long as feasible, or on a regular basis during the active growing season
to promote flowering and seed set. Survival is high in increase
plantings receiving proper care, but lower on sites with existing
vegetation (Skinner, 2003).

#####  {#section-2 .Header-3}

##### Management {#management .Header-3}

There is a high potential for using this species to revegetate alpine
and subalpine disturbances, and in other degraded areas of the western
U.S (Wasser, 1982). New seedings may need protection from trampling and
weeds during establishment. Clipping weeds above the seedlings is a
preferred method of weed suppression as there are no herbicides
selective for broadleaf plants. Western yarrow vigor, aesthetics, and
stand persistence after establishment may be sustained with properly
timed grazing or defoliation of associated species. Satisfactory control
of western yarrow is achieved through herbicide application mixtures of
dicamba and dichlorprop (Robocker, 1977). Always consult product label
prior to application and properly follow recommendations.

#####  {#section-3 .Header-3}

##### Pests and Potential Problems {#pests-and-potential-problems .Header-3}

Inflorescences that are harvested for seed production often contain
small quantities of insect larvae and numerous live insects. Many
beneficial and pollinating insects, such as minute pirate bug (*Orius*),
big-eyed bug (*Geocoris*), hoverflies (Syrphidae), and several tachnid
flies (*Archytas apicifer*, *Gymnosoma*, *Tricopoda pennipes,
Cylindromia*) are known to frequent yarrow plants (Long, 2001). Pest
insects include common leaf bugs (*Lygus*) and flea beetles
(Chrysomelidae). Root rot and mildew may occur in poorly drained soils
(Warwick and Black, 1982).

##### Environmental Concerns {#environmental-concerns .Header-3}

Western yarrow is a pioneer species and considered an increaser where
the forage resource has been overstocked and excessively utilized. It
should be considered noninvasive when used within a diverse plant
community in its anticipated area of adaptation.

#####  {#section-4 .Header-3}

##### Seed Production  {#seed-production .Header-3}

Production fields should be seeded at a rate of 25 PLS per linear foot
of row (82 per linear meter of row). Between-row spacing is dependent on
the type of planting and cultivation equipment, and ranges from 22 to 36
in. (56 to 90 cm). Adequate between-row space should be provided to
perform mechanical cultivation. At 24-in. row spacing, the recommended
seeding rate is 0.12 PLS lb/acre (0.14 kg/ha), and at 30- and 36-in. row
spacing, the seeding rate is 0.09 and 0.08 PLS lb/acre (0.1 and 0.09
kg/ha), respectively. There are presently no herbicides specifically
labeled to control weeds in seed production fields. Seed harvest can be
accomplished by swathing and combining from the cured windrows, or
direct combining. The indeterminate ripening may necessitate periodic
mechanical stripping as seed heads mature.

Seed is processed over a two-to three-screen fanning mill (slotted mesh
screens), with final cleaning over an indent cylinder or gravity table.
An acceptable seed quality testing standard is 95 percent purity and 80
percent viability (Stevens and Meyer, 1990). Seed production of 100 to
150 lb/acre (112 to 170 kg/ha) can be expected under irrigated
conditions. Seed longevity is at least 5 years when stored at moderate
temperatures and low humidity (USDA NRCS, 2004).

#####  {#section-5 .Header-3}

##### Cultivars, Improved, and Selected Materials (and area of origin) {#cultivars-improved-and-selected-materials-and-area-of-origin .Header-3}

Great Northern Germplasm is a selected class release of western yarrow
originally collected in 1988 in Flathead County, Montana. This 2004
release was selected for top performance in vigor, height, seedhead
production, and survival from among 29 accessions of native yarrows from
Montana and Wyoming. It is adapted for use in northern Idaho, and all of
Montana and Wyoming, except the Red Desert and Bighorn Basin. G~1~ seed
(analogous to Foundation seed) will be maintained by the USDA NRCS
Bridger Plant Materials Center and is available to commercial growers
through the Foundation Seed Program at Montana State University-Bozeman
and the University of Wyoming Foundation Seed Service at Powell,
Wyoming. Commercial production is limited to two generations beyond
G~1~.

Yakima Germplasm is a source-identified, composite release of western
yarrow from 27 collection sites on the U.S. Army Yakima Training Center
in Yakima, Washington. Yakima Germplasm western yarrow is intended for
use in the rehabilitation and restoration of western rangelands. The
USDA-ARS Forage and Range Research Laboratory, Logan, Utah, will
maintain G~1~ seed and it will be made available to growers through the
Utah Crop Improvement Association. Seed through the G~4~ generation will
be eligible for certification.

##### References {#references .Header-3}

Airhart, D.L. 1988. *Experiments with seed-grown sod as plant
introduction technique described (Massachusetts)*. Restoration &
Management Notes, 6(1):51.

Anderson, K.L., E.F. Smith, and C.E. Owensby. 1970. *Burning bluestem
range*. Journal of Range Management 23:81-92.

Bartos, D.L. and W.F. Mueggler. 1981. *Early succession in aspen
communities following fire in western Wyoming*. Journal of Range
Management 34(4):315-318.

Bostock, S.J. and R.A. Benton. 1979. *The reproductive strategies of
five perennial Compositae*. Journal of Ecology 67:91-107.

Bourdot, G.W. 1984. *Regeneration of yarrow (Achillea millefolium L.)
rhizome fragments of different length for various depths in the soil*.
Weed Research 24: 421-429.

Bourdot, G.W., D.J. Saville, and R.J. Field. 1984. *The response of
Achillea millefolium L. (Yarrow) to shading*. New Phytologist
97:653-663.

Bourdot, G.W., R.J. Field, and J.G.H. White. 1985. *Growth analysis of
Achillea millefolium L. (Yarrow) in the presence and absence of a
competitor\--Hordeum vulgare L. (Barley).* New Phytologist 101:507-519.

Budd A.C. and J.B. Campbell. 1959. *Flowering sequence of a local
flora*. Journal of Range Management 12: 127-132.

Callan, N. (December) 2002. *Personal communication*. Montana State
University. Western Agricultural Research Station, Corvallis, MT.

Clausen, J., D.D. Keck, and W.M. Hiesey. 1958. *Experimental studies on
the nature of species: III. Environmental responses of climatic races of
Achillea*. Carnegie Institution of Washington Publication 581,
Washington D.C.

Cronquist, A., A.H. Holmgren, N.H. Holmgren, and J.L. Reveal. 2002.
*Intermountain Flora, vascular plants of the intermountain west, Vol. 5:
The Asterales*. The New York Botanical Garden, NY.

Hiesey, W.M. and M.A. Nobs. 1970. *Genetic and transplant studies on
contrasting species and ecological races of the Achillea milllefolium
complex*. Botanical Gazette 131(3):245-259.

Higgins, S.S. and R.N. Mack. 1987. *Comparative responses of Achillea
millefolium ecotypes to competition and soil type*. Oecologia 73:591-597

Hitchcock, C.L., A. Cronquist, M. Ownbey, and J.W. Thompson. 1955.
*Vascular plants of the Pacific Northwest*. University of Washington
Press, Seattle and London.

Hitchcock, C.L. and A. Cronquist. 1973. *Flora of the Pacific Northwest:
an illustrated manual*. University of Washington Press, Seattle and
London.

Kannangara, H.W. and R.J. Field. 1985. *Environmental and physiological
factors affecting the fate of seeds of yarrow (Achillea millefolium) in
arable land in New Zealand*. Weed Research. 25:87-92.

Johnson, J.R. and G.E. Larson. 1999. *Grassland Plants of South Dakota
and the Northern Great Plains*. South Dakota State University. College
of Agriculture and Biological Sciences. South Dakota Agricultural
Experiment Station, Bulletin 566 (revised).

Lavin, M. (November) 2002. *Personal communication*. Montana State
University, Bozeman.

Lesica, P. (June) 2001. *Personal communication*. Conservation Biology
Research. Missoula, MT.

Long R. F. 2001. *Quantifying pests and beneficial insects in insectary
hedgerows-the final report*.
http:www.sarep.ucdavis.edu/grants/Reports/Long/Long99-22-2/htm

Luna, T., J. Evans, and D. Wick. 2004. *Propagation protocol for
production of container Achillea millefolium L. Nutt. (172 ml
conetainers); Glacier National Park, West Glacier, MT*. *In:* Native
Plant Network. URL:
[http://www.nativeplantnetwork.org](http://www.nativeplantnetwork.org/)/
Moscow, Idaho: University of Idaho, College of Natural Resources, Forest
Research Nursery.

Monsen, S.B., R. Stevens, and N.L. Shaw, comps. 2004. *Restoring western
ranges and wildlands*. Gen. Tech. Rep. RMRS-GTR-136-vol-2. Fort Collins,
CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain
Research Station. Pages 295-698 plus index.

Reitz, L.P. and H.E. Morris. 1939. *Important grasses and other common
plants on Montana ranges\--description, distribution, and relative
value*. Bulletin 375. Montana State College, Agricultural Experiment
Station, Bozeman.

Robinson, B.L. and M.L. Fernald. 1908. *Gray\'s New Manual of Botany: A
handbook of the flowering plants and ferns*. Amer. Book Co., New York.

Robocker, W.C. 1977. *Germination of seeds of common yarrow (Achillea
millefolium) and its herbicidal control*. Weed Science 25(5):456-459.

Skinner, D.M. 2003. *Propagation protocol for production of container
Achillea millefolium L ; Pullman Plant Materials Center, Pullman,
Washington*. *In:* Native Plant Network. URL:
[http://www.nativeplantnetwork.org](http://www.nativeplantnetwork.org/)/
Moscow, Idaho: University of Idaho, College of Natural Resources, Forest
Research Nursery.

Sorenson, J.T. and D.J. Holden. 1974. *Germination of native prairie
forb seeds*. Journal of Range Management 27(2):123-126.

Stevens, R. and S.E. Meyer. 1990*. Seed quality testing for range and
wildland species*. Rangelands 12(6):341-346.

Taylor, R.J. 1992. *Sagebrush country: A wildflower sanctuary*. Mountain
Press Publishing Company. Missoula, MT.

USDA FS. 1937. *Range plant handbook*. Washington, DC.

USDA FS. 1966. *Notes on western range forbs\--Cruciferae through
Compositae*. Agriculture Handbook No. 293. Washington, DC.

USDA NRCS. 2004. *Release notice for selected class of Great Northern
Germplasm western yarrow*. Bridger, MT.

USDA SCS. 1976. *Climax vegetation of Montana based on soils and
climate*. Bozeman, MT.

Warwick, S.I. and L. Black. 1982. *The biology of Canadian weeds.
Achillea millefolium L*.

Canadian Journal of Plant Science. 62:163-182.

Wasser, C.H. 1982. *Ecology and culture of selected species useful in
revegetating disturbed lands in the West*. USFWS FWS/OBS-82/56. 347 pp.

Whitson, T.D., L.C. Burrill, S.A. Dewey, D.W. Cudney, B.E. Nelson, R.D.
Lee, and Robert

Parker. 1991. *Weeds of the West*. The Western Society of Weed Science
and University of

Wyoming, Laramie.

##### Prepared By & Species Coordinator:  {#prepared-by-species-coordinator .Header-3}

*Susan R. Winslow*

USDA NRCS, Plant Materials Center, Bridger, Montana

##### Edited: 24Jan2006 jsp; 30may06jsp {#edited-24jan2006-jsp-30may06jsp .Header-4}

For more information about this and other plants, please contact your
local NRCS field office or Conservation District, and visit the PLANTS
Web site\<[http://plants.usda.gov](http://plants.usda.gov/)\> or the
Plant Materials Program Web site
\<[http://Plant-Materials.nrcs.usda.gov](http://Plant-Materials.nrcs.usda.gov/)\>

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