Achillea millefolium

Yarrow is a perennial herb that can spread both by seed and by means of creeping stems, known as stolons (2). The flowers, which are present from June to September (7) are visited by a huge range of insects (2). The whole plant has a strongly aromatic scent (2). Yarrow was once held in high esteem as a medicinal plant, and has been used to staunch wounds and to ward off illness and bad luck (6). Conversely it was believed to be one of the Devil's herbs, and was used in divination (4). It was also said to cause nosebleeds if a leaf was put into the nostril, and the plant was known as 'nosebleed' in some areas (4). In East Anglia, this property of the plant was employed in order to divine future love; a leaf was placed inside the nose and the following rhyme was recited: 'Yarroway, yarroway, bear a white blow, if my love love me, my nose will bleed now' (4). The leaves and flowers have a bitter, astringent and pungent taste; the alternative common name 'old man's pepper' refers to this quality (7).

Yarrow is a common herb that has been highly regarded for its medicinal properties in Britain since Anglo-Saxon times (4). The erect stems are woolly and the dense, flattened flower-heads are typically white, but more rarely they may be pink or reddish (2). The leaves are deeply divided, forming many small lobes (5); this feature is referred to by the specific Latin name, millefolium, which means 'thousand leaf' (6). The name of the genus, Achillea is thought to have arisen as it is said that Achilles used this herb to treat the wounds of his soldiers. The common name 'yarrow' derives from the Anglo-Saxon name for the plant, 'gearwe' (7).

Strongly aromatic perennial herb. Leaves deeply 2-3 pinnate with linear-subulate ultimate segments. Inflorescence terminal, large, branched, flat-topped consisting of numerous small capitula. Capitula white to pale mauve-lilac. Some cultivated hybrids have other colour forms.

Achillea millefolium has pollen classified as trizonocolporate, with a lacunate aperture and echinate sculpturing. (Meo & Khan, 2003.)

Achillea millefolium was first described by Linnaeus in Species Plantarum in 1853.

A. millefolium is a perennial herb that usually spreads via rhizome. It is characterized by feathered leaves, proximally petiolate and distally sessile, that gradually reduce in size as they approach the apex of the plant. The ray flowers can range from white to pink to dark purple, but the disc flowers are always white or grayish white. It has a variety of ploidy levels, from 2n = 18 to 2n = 72. Because of its huge degree of variability, it has often been treated as several distinct species or as one species with several varieties. It has one of the most expansive ranges, growing in virtually every corner of North America. This may be due to its ability to tolerate meadows and woodlands, dry or damp soils, and to accomodate altitudes from sea level to 3600 m. In fact, much observable variation in A. millefolium can be contributed to environmental differences.

General: Sunflower Family (Asteraceae). Common yarrow is a perennial herb that produces one to several stems (2-10 dm tall) from a fibrous underground horizontal rootstock (rhizome). It is known to be both native and introduced. Leaves are evenly distributed along the stem, with the leaves near the middle and bottom of the stem being the largest. The leaves have varying degrees of hairiness (pubescence). Leaf blades are lanceolate in outline, but bipinnately dissected. Overall leaf dimensions range from 0.5-3 cm wide by 3-15 cm long. The flower heads (inflorescence) have a flattened dome shape corymbiform (2.5-4 mm thick by 4-5 mm high) with approximately 10-20 ray flowers. The flowers are whitish to yellowish-white. The plant commonly persists from May through June.

Distribution: For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Habitat: The plant is frequently found in the mildly disturbed soil of grasslands and open forests.

Milfoil

More info for the term: adventitious

Western yarrow is circumboreal. In North America, it occurs in every state, province, and in Mexico [19,33]. It is adventitious in Hawaii [62].

Achillea pecten-veneris Pollard:
Mexico (Mesoamerica)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea occidentalis (DC.) Raf. ex Rydb.:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea lanulosa subsp. lanulosa :
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea lanulosa subsp. alpicola (Rydb.) D.D. Keck:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea borealis subsp. arenicola (A. Heller) D.D. Keck:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea borealis subsp. californica (Pollard) D.D. Keck:
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea palmeri Rydb.:
Mexico (Mesoamerica)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Achillea millefolium L.:
Argentina (South America)
Australia (Oceania)
Canada (North America)
Brazil (South America)
Chile (South America)
Costa Rica (Mesoamerica)
Colombia (South America)
Mexico (Mesoamerica)
Honduras (Mesoamerica)
Greenland (North America)
Guatemala (Mesoamerica)
Mongolia (Asia)
Ecuador (South America)
Nicaragua (Mesoamerica)
New Zealand (Oceania)
United States (North America)
South Africa (Africa & Madagascar)
Peru (South America)
China (Asia)
Russian Federation (Asia)
Venezuela (South America)
Caribbean (Caribbean)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Native to Europe and W Asia; introduced in many other countries.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Achillea millefolium spans the entire continental U.S. (including Alaska) and every Canadian province.

For more information, see the map above provided by Flora of North America. (Trock, 2006.)

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

This very common plant occurs throughout the British Isles (5). Elsewhere it is found in Europe and western Asia, and has been introduced to North America, Australia and New Zealand (2).

More info for the terms: duff, forb

Western yarrow is a perennial forb 11 to 40 inches (30-100 cm) in height with extensive rhizomes. It has few to numerous erect stems. The basal rosette of leaves may remain green throughout the winter [43]. Plants grow in a somewhat scattered fashion and seldom form pure stands in areas larger than 5 square meters [69]. Typical European Achillea millefolium is hexaploid with flat leaves. Native forms are mostly tetraploid, with narrow leaf-segments disposed in various planes so that the leaf is 3-dimensional [33].

McLean [49] reported that in a Douglas-fir (Pseudotsuga menziesii) forest zone in British Columbia, the fibrous roots and rhizomes of yarrow grew mostly in the duff layer or between it and the mineral soil.

Perennials, 6–65+ cm (usually rhizomatous, sometimes stoloniferous). Stems 1(–4), erect, simple or branched, densely lanate-tomentose to glabrate. Leaves petiolate (proximally) or sessile (distally, weakly clasping and gradually reduced); blades oblong or lanceolate, 3.5–35+ cm × 5–35 mm, 1–2-pinnately lobed (ultimate lobes ± lanceolate, often arrayed in multiple planes), faces glabrate to sparsely tomentose or densely lanate. Heads 10–100+, in simple or compound, corymbiform arrays. Phyllaries 20–30 in ± 3 series, (light green, midribs dark green to yellowish, margins green to light or dark brown) ovate to lanceolate, abaxial faces tomentose. Receptacles convex; paleae lanceolate, 1.5–4 mm. Ray florets (3–)5–8, pistillate, fertile; corollas white or light pink to deep purple, laminae 1.5–3 × 1.5–3 mm. Disc florets 10–20; corollas white to grayish white, 2–4.5 mm. Cypselae 1–2 mm (margins broadly winged). 2n = 18, 27, 36, 45, 54, 63, 72 (including counts from Europe).

Erect, up to 1 m tall, basally woody shrublet with obtuse-angled, punctate-glandulose, woolly pilose twigs. Leaves long-petiolate, green, homomorphic, cauline akin to basal, laxly to densely long soft hairy, linear-lanceolate to oblong, up to 20 x 1 – 4 cm, smaller above, punctate-glandulose, 2–3-pinnatisect, rachis 0.4 – 1.5 mm wide; primary segments numerous, linear to linear-lanceolate; ultimate segments narrowly linear filiform, 0.2 – 0.5 (-1) mm wide, cartilaginous mucronate. Capitula 5 – 6 mm across, up to 150 or sometimes more, on 2 – 5 mm long peduncles, in 5 – 15 cm broad compound corymbs. Involucre oblong to ovoid, 4.5 – 5 x 2.5 – 4 mm, basally rotundate, phyllaries oblong to lanceolate, ± acute to obtuse and laciniate, rarely carinate, pink to brownish scarious on margins. Paleae whitish membranous, with green midrib, lanceolate, obtuse and ± fimbriate, upwards pilose. Ray-florets 4 – 6, with whitish or pale-white, 3-lobed, 1.5 – 2.5 x 1.5 – 3 mm, reflexed limb. Disc-florets 10 – 20, with 2 – 3 mm long, 5-toothed corolla tube. Cypselas oblong, ± flattened, c. 2.5 mm long, glaucous-glabrous, epappose.

Achillea alpicola (Rydberg) Rydberg; A. arenicola A. Heller; A. borealis Bongard subsp. arenicola (A. Heller) D. D. Keck; A. borealis subsp. californica (Pollard) D. D. Keck; A. californica Pollard; A. gigantea Pollard; A. lanulosa Nuttall; A. lanulosa subsp. alpicola (Rydberg) D. D. Keck; A. laxiflora Pollard & Cockerell; A. megacephala Raup; A. millefolium var. alpicola (Rydberg) Garrett; A. millefolium var. arenicola (A. Heller) Nobs; A. millefolium var. asplenifolia (Ventenat) Farwell; A. millefolium subsp. borealis (Bongard) Breitung; A. millefolium var. borealis (Bongard) Farwell; A. millefolium var. californica (Pollard) Jepson; A. millefolium var. gigantea (Pollard) Nobs; A. millefolium subsp. lanulosa (Nuttall) Piper; A. millefolium var. lanulosa (Nuttall) Piper; A. millefolium var. litoralis Ehrendorfer ex Nobs; A. millefolium var. maritima Jepson; A. millefolium var. megacephala (Raup) B. Boivin; A. millefolium var. nigrescens E. Meyer; A. millefolium var. occidentalis de Candolle; A. millefolium var. pacifica (Rydberg) G. N. Jones; A. millefolium var. puberula (Rydberg) Nobs; A. nigrescens (E. Meyer) Rydberg; A. occidentalis (de Candolle) Rafinesque ex Rydberg; A. pacifica Rydberg; A. puberula Rydberg; A. rosea Desfontaines; A. subalpina Greene

The feathered leaves of Achillea millefolium resemble those of Anthemis cotula (mayweed chamomile), Matricaria discoidea (pineapple weed) and Daucus carota (wild carrot), though all can easily be distinguished by their blooms. (Calhoun, 2010.) Conversely, the flowers of A. millefolium are easily confused with those of Lepidium latifolium (perennial pepperweed) and Cardaria draba (hoary cress). The highly divided leaves of A. millefolium allow for distinction from these look-alikes. (Donaldson, 2004.)

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This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

101  Bluebunch Wheatgrass

102  Idaho Fescue

103  Green Fescue 

104  Antelope Bitterbrush-Bluegrass Wheatgrass

105  Antelope Bitterbrush-Idaho Fescue

107  Western Juniper-Big Sagebrush

109  Ponderosa pine shrubland

110  Ponderosa Pine-Grassland

204  North Coastal Shrub

309  Idaho Fescue-Western Wheatgrass

315  Big Sagebrush-Idaho Fescue

316  Big Sagebrush-Rough Fescue

317  Bitterbrush-Bluebunch Wheatgrass

323  Shrubby Cinquefoil-Rough Fescue

401  Basin Big Sagebrush

402  Mountain Big Sagebrush

409  Tall Forb

411  Aspen Woodland

413  Gambel Oak

608  Wheatgrass-Grama-Needlegrass

610  Wheatgrass

613  Fescue Grassland

805  Riparian

910  Hairgrass

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K011  Western ponderosa forest

K012  Douglas-fir forest

K015  Western spruce-fir forest

K016  Eastern ponderosa forest

K018  Pine-Douglas-fir forest

K019  Arizona pine forest

K021  Southwestern spruce-fir forest

K023  Juniper-pinyon woodland

K037  Mountain mahogany-oak scrub

K038  Great Basin sagebrush

K040  Saltbush-greasewood

K049  Tule marshes

K051  Wheatgrass-bluegrass

K052  Alpine meadows and barren

K055  Sagebrush steppe

K056  Wheatgrass-needlegrass shrubsteppe

K063  Foothills prairie

K064  Grama-needlegrass-wheatgrass

K065  Grama-buffalograss

K066  Wheatgrass-needlegrass

K067  Wheatgrass-bluestem-needlegrass

K070  Sandsage-bluestem prairie

K074  Bluestem prairie

K098  Northern floodplain forest

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES17  Elm-ash-cottonwood

FRES20  Douglas-fir

FRES21  Ponderosa pine

FRES23  Fir-spruce

FRES29  Sagebrush

FRES30  Desert shrub

FRES34  Chaparral-mountain shrub

FRES35  Pinyon-juniper

FRES36  Mountain grasslands

FRES38  Plains grasslands

FRES39  Prairie

FRES41  Wet grasslands

FRES44  Alpine:

A. millefolium occupies many diverse habitats, including sunny pastures, meadows and roadsides with dry soils, stream sides and waste grounds with sandy or salty soils, and damp woodlands with clay soils. (Trock, 2006.) There is, however, some morphological variation (eco-morphotypes or ecotypes) among the species that is dependent on its habitat.

Grows in most types of grassland habitat, including coastal sand dunes, lawns, road verges, waste ground and montane grasslands. It grows in all types of soil, save for the most nutrient poor, and is drought tolerant (3).

Common yarrow is a drought tolerant species of which there are several different ornamental cultivars. Plant the seeds no more than ¼ inch deep due to the need of light for germination. The seeds also require a temperature range of 65-75 degrees Fahrenheit. Common yarrow responds best to soil that is poorly developed and well drained. The plant has a relatively short life. To prolong the life of the plant, divide the plant every other year and plant 12-18 inches apart. Common yarrow is a weedy species and can become invasive. Proper care should be used to control the spread of the plant from its desired growing location.

Achillea millefolium (Yarrow) introduced
(Bees suck nectar or collect pollen; flies and beetles suck nectar or feed on pollen; other insects suck nectar; some observations are from Graenicher, Reed, Grundel & Pavlovic, Krombein et al., and Mawdsley as indicated below, otherwise they are from Robertson)

Bees (long-tongued)
Apidae (Bombini): Bombus auricomus cp; Anthophoridae (Ceratinini): Ceratina sp. (Re), Ceratina dupla dupla sn cp (Gr); Anthophoridae (Nomadini): Nomada cuneatus sn; Megachilidae (Megachilini): Megachile centuncularis sn cp (Gr), Megachile petulans cp

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon texanus texanus (Re), Agapostemon virescens (Re), Augochlorella striata sn cp (Gr), Halictus (or Lasioglossum) sp. sn cp (Gr), Halictus confusus (Re), Halictus ligatus sn cp (Rb, Gr, Re), Lasioglossum cressonii sn cp (Gr), Lasioglossum imitatus sn cp (Gr), Lasioglossum pectoralis (Re), Lasioglossum perpunctatus (Re), Lasioglossum pilosus pilosus sn cp (Rb, Gr), Lasioglossum tegularis sn cp (Gr), Lasioglossum versatus sn cp fq (Rb, Gr), Paralictus simplex sn; Colletidae (Hylaeinae): Hylaeus mesillae sn (Gr, Kr), Hylaeus modestus modestus sn (Gr, Kr), Hylaeus saniculae (Kr); Andrenidae (Andreninae): Andrena integra (Kr), Andrena miranda (Kr), Andrena nigrifrons (Kr); Andrenidae (Panurginae): Calliopsis andreniformis (Kr)

Wasps
Sphecidae (Crabroninae): Anacrabro ocellatus (Gr), Ectemnius continuus (Re), Ectemnius dives (Gr), Ectemnius lapidarius (Gr), Ectemnius maculosus (Gr), Ectemnius rufifemur, Ectemnius trifasciatus (Gr), Oxybelus emarginatus, Oxybelus mexicanus, Oxybelus niger (Gr), Oxybelus packardii, Oxybelus uniglumis (Gr); Sphecidae (Philanthinae): Cerceris clypeata (Gr), Cerceris compacta, Cerceris rufinoda, Philanthus bilunatus (Gr), Philanthus politus (Re); Gasteruptiidae: Gasteruption assectator (Gr); Leucospididae: Leucospis affinis (Gr); Perilampidae: Perilampus hyalinus (Gr, Re); Vespidae (Eumeninae): Ancistrocerus adiabatus (Gr), Eumenes fraterna (Gr), Euodynerus foraminatus, Parancistrocerus fulvipes, Parancistrocerus pensylvanicus (Gr), Symmorphus cristatus (Gr)

Flies
Tabanidae: Chrysops striatus sn; Nemestrinidae: Neorhynchocephalus sackenii sn; Empididae: Rhamphomyia sp. sn (Gr); Stratiomyidae: Hedriodiscus vertebrata (Gr), Nemotelus nigrinus (Gr), Odontomyia cincta (Gr), Odontomyia virgo (Gr), Stratiomys normula (Gr), Stratiomys obesa (Re); Bombyliidae: Ogcodocera leucoprocta sn, Toxophora amphitea sn; Syrphidae: Allograpta obliqua sn (Rb, Gr), Epistrophe xanthostoma (Gr), Eristalinus aeneus sn, Eristalis arbustorum sn (Rb, Gr), Eristalis barda (Re), Eristalis brousii (Gr), Eristalis dimidiatus sn, Eristalis tenax sn (Rb, Gr), Eristalis transversus sn (Rb, Gr), Eupeodes americanus sn (Rb, Gr), Helophilus chrysostomus (Gr), Mallota bautias sn, Orthonevra nitida sn, Paragus tibialis sn, Sphaerophoria contiqua sn (Rb, Gr), Syritta pipiens sn (Rb, Gr), Syrphus ribesii sn, Toxomerus geminatus (Gr), Toxomerus marginatus sn (Rb, Gr, Re); Conopidae: Physoconops brachyrhynchus sn, Thecophora abbreviata (Gr), Thecophora occidensis sn; Tachinidae: Archytas analis sn (Rb, Gr), Cylindromyia carolinae (Gr), Epigrimyia polita sn (Rb, Gr), Gymnosoma fuliginosus sn, Gymnoclytia immaculata sn (Rb, Gr), Gymnoclytia occidua sn, Periscepsia laevigata sn; Sarcophagidae: Helicobia rapax sn (Rb, Gr), Ravinia anxia sn, Sarcophaga spp. (Gr), Senotainia rubriventris sn, Sphixapata trilineata sn; Calliphoridae: Lucilia sp. (Gr), Lucilia illustris (Gr), Phormia regina (Gr), Pollenia rudis (Gr); Muscidae: Graphomya maculata (Gr), Helina evecta (Gr), Morellia micans (Gr), Neomyia cornicina sn; Anthomyiidae: Anthomyia sp. (Gr), Calythea pratincola (Gr), Delia platura sn (Rb, Gr); Fanniidae: Fannia manicata sn; Sepsidae: Themira putris (Gr); Lauxaniidae: Camptoprosopella vulgaris sn

Butterflies
Nymphalidae: Limenitis arthemis astyanax (Gr), Phyciodes tharos (Re); Lycaenidae: Lycaeides melissa samuelis (GP), Satyrium calanus (Gr), Satyrium edwardsii (Re)

Skippers
Hesperiidae: Euphyes vestris (Re)

Moths
Pterophoridae: Geina tenuidactylus (Gr), Emmelina monodactyla (Gr)

Beetles
Cerambycidae: Euderces picipes (Gr); Cleridae: Trichodes apivorus (Gr), Trichodes nutalli (Mwd); Mordellidae: Mordella melaena sn, Mordellistena comata (Gr); Scarabaeidae: Trichiotinus piger (Gr)

Plant Bugs
Lygaeidae: Lygaeus turcicus (Gr), Neacoryphus bicrucis (Gr); Miridae: Adelphocoris rapidus (Gr), Cimex ruficornis (Gr), Lygus lineolaris (Gr)

Achillea millefolium is a source of nectar for many species of flies, wasps and a few bees. Some grasshoppers, aphids, beetles and caterpillars may feed on it.

Achillea millefolium is subject to powdery mildew, root and stem rot.

Rare

More info for the term: rhizome

Western yarrow regenerates from fragments of rhizomes and from colonization through short-distance (1-2 m) wind dispersal of seeds [15,47,61]. In disturbed soils, fragmented rhizomes regenerate shoots which can emerge from soil depths as great as 12 inches (30 cm). In undisturbed soil the rhizomes remain attached to the parent plant, forming new plants at the rhizome apices [15].

The fruit is a small achenes weighing about 0.17 mg. They are produced in large numbers. Several thousand achenes may be produced per flowering stem. The viability of freshly shed seeds exceeds 90%. Western yarrow seed showed 41% germination after 9 years in dry storage [15].

More info on this topic.

More info for the term: hemicryptophyte

Hemicryptophyte

More info for the term: forb

Forb

Achillea millefolium has different flowering periods depending on where it's located. In the south, it flowers late April to early July, but in the north it doesn't begin flowering until mid-July and will continue through mid-September. (Trock, 2006.)

Perennial

Axillary rhizomes of A. millefolium produce new plants annually at their apices. Vegetative reproduction occurs when the rhizomes are fragmented. (Bourdot, Field & White, 1985.)

Achillea millefolium has a moderate growth rate.

According to a 2008 study, A. millefolium has travelled from Europe and southwest Asia to east Asia, then to North America. The A. millefolium aggregate has been shaped by cycles of differentiation, hybridization and polyplodization, resulting in the now worldwide expanse of the hexaploid (and other polyploids). (Guo, Saukel & Ehrendorfer, 2008.)

The chromosome number of A. millefolium varies, and has been observed as 2n = 18, 27, 36, 45, 54, 63, 72. (Trock, 2006.)

In the Western US, the tetraploid (2n=36) and the hexaploid (2n=54) are the dominant ploidy levels. (Tyrl, 1969.) Capable of hybridization between ploidies, A. millefolium has been observed at every ploidy level up to octoploid (2n=72) worldwide.

The morphological variant previously recognized as Achillea Borealis or Achillea millefolium var. Borealis is a species of special concern in Canada. (USDA, 2010.) Similarly, the eco-morphotype previously known as A. megacephala or A. millefolifum var. megacephala is of special concern in Canada. (Trock, 2006.)

Rounded Global Status Rank: T1 - Critically Imperiled

Canada

Rounded National Status Rank: N1 - Critically Imperiled

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread in grasslands and open woods, throughout Great Plains. Natural range is wide, but some populations may be introduced.

Common and widespread: not threatened (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).

This species is not threatened.

Common yarrow may suffer from mildew or root rot if not planted in well-drained soil.

More info for the term: rhizome

Western yarrow tends to increase rapidly in disturbed areas or overgrazed rangelands,
replacing more valuable forage species and crops [43]. It is often an indicator of past
overstocking and excessive utilization [69]. Western yarrow tends to decrease on
grazing plots once grazing has ceased [7,20]. Since
rhizomes are a major means
of western yarrow regeneration, starting control measures early in autumn may prevent
spring growth from autumn and winter rhizome dry matter [15].
In New Zealand, barley (Hordeum vulgare) reduced rhizome and seed production
in western yarrow [15].

Dicamba and mixtures with triclopyr are effective in controlling western yarrow [74].

Although A. millefolium contains alkaloids and other volatile compounds, it is not considered toxic because it is so rarely consumed by livestock. (US Forest Service, 2010.)

Conservation action is not required for this very common species.

Please contact your local agricultural extension specialist or county weed specialist to learn what works best in your area and how to use it safely. Always read label and safety instructions for each control method. Trade names and control measures appear in this document only to provide specific information. USDA, NRCS does not guarantee or warranty the products and control methods named, and other products may be equally effective.

These materials are readily available from commercial plant sources.

This plant may become weedy or invasive in some regions or habitats and may displace desirable vegetation if not properly managed. Please consult with your local NRCS Field Office, Cooperative Extension Service office, or state natural resource or agriculture department regarding its status and use. Weed information is also available from the PLANTS Web site at plants.usda.gov.

Achillea millefolium has a long history of cultural and medicinal uses. In some eastern cultures it has been used in the mystical practice of divination. A. millefolium can be distilled to form an oil that possesses known anti-inflammatory and blood-staunching abilities. It has been used to treat internal bleeding, excessive menstrual bleeding, high blood pressure, fever reduction and more. The leaves have been used, both fresh and dry, as a garnish and in salads. (Morgenstern, 2010.)

Caution: This plant may become invasive.