Achillea millefolium, commonly known as yarrow/ˈjæroʊ/ or common yarrow is a flowering plant in the familyAsteraceae. It is native to temperate regions of the Northern Hemisphere in Asia, Europe, and North America. It has been introduced as a feed for livestock in places like New Zealand and Australia, where it is a common herb of both wet and dry areas, such as roadsides, meadows, fields and coastal places.
In New Mexico and southern Colorado, it is called plumajillo (Spanish for 'little feather') from its leaf shape and texture. In antiquity, yarrow was known as herbal militaris, for its use in stanching the flow of blood from wounds. Other common names for this species include gordaldo, nosebleed plant, old man's pepper, devil's nettle, sanguinary, milfoil, soldier's woundwort, thousand-leaf, and thousand-seal.
Clusters of 15 to 40 tiny disk flowers surrounded by three to eight white to pink ray flowers are, in turn, arranged in a flat-topped inflorescence (Wenatchee Mountains, Washington).
Achillea millefolium is an erect, herbaceous, perennial plant that produces one to several stems 0.2–1 m (0.66–3.28 ft) in height, and has a spreading rhizomatous growth form. 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). The leaves are 5–20 cm (2.0–7.9 in) long, bipinnate or tripinnate, almost feathery, and arranged spirally on the stems. The leaves are cauline, and more or less clasping.
The inflorescence has 4 to 9 phyllaries and contains ray and disk flowers which are white to pink. The generally 3 to 8 ray flowers are ovate to round. Disk flowers range from 15 to 40. The inflorescence is produced in a flat-topped capitulum cluster and the inflorescences are visited by many insects, featuring a generalized pollination system. The small achene-like fruits are called cypsela.
Achillea millefolium after a wildfire in the Wenatchee foothills, Washington.
Yarrow grows from sea level to 3,500 metres (11,500 ft) in elevation. The plant commonly flowers from May to July. Common yarrow is frequently found in the mildly disturbed soil of grasslands and open forests. Active growth occurs in the spring.
The plant is native to Eurasia and is found widely from the UK to China.
In North America, both native and introduced genotypes, and both diploid and polyploid plants are found. It is found in every habitat throughout California except the Colorado and Mojave Deserts. Common yarrow produces an average yield of 43,000 plants per acre, with a total dry weight of 10,500 lbs.
The plant is found in Australia as an introduction.
Achillea millefolium var. occidentalis – North America
Achillea millefolium var. pacifica – west coast of North America, Alaska
Achillea millefolium var. puberula – endemic to California
Several cavity-nesting birds, including the common starling, use yarrow to line their nests. Experiments conducted on the tree swallow, which does not use yarrow, suggest that adding yarrow to nests inhibits the growth of parasites.
For propagation, seeds require light for germination, so optimal germination occurs when planted no deeper than one-quarter inch (6 mm). Seeds also require a germination temperature of 18–24 °C (64–75 °F). It has a relatively short life in some situations, but may be prolonged by division in the spring every other year, and planting 12 to 18 in (30–46 cm) apart. It can become invasive.
The species use in traditional gardens has generally been superseded by cultivars with specific 'improved' qualities. Some are used as drought tolerant lawn replacements, with periodic mowing. The many different ornamental cultivars include: 'Paprika', 'Cerise Queen', 'Red Beauty', 'Red Velvet', 'Saucy Seduction', 'Strawberry Seduction' (red), 'Island Pink' (pink), and 'Calistoga' (white), and 'Sonoma Coast' (white). Several, including 'Kelwayi', and 'Lansdorferglut' (both pink) have gained the Royal Horticultural Society's Award of Garden Merit. The many hybrids of this species designated Achillea x taygetea are useful garden subjects, including: 'Appleblossom', 'Fanal', 'Hoffnung', and 'Moonshine'.
Yarrow (Achillea millefolium) essential oil in a colorless glass vial
A. millefolium can be planted to combat soil erosion due to the plant's resistance to drought. Before the arrival of monocultures of ryegrass, both grass leys and permanent pasture always contained A. millefolium at a rate of about 0.3 kg/ha. At least one of the reasons for its inclusion in grass mixtures was its deep roots, with leaves rich in minerals. Thus its inclusion helped to prevent mineral deficiencies in the ruminants to which it was fed.
It was introduced into New Zealand as a drought-tolerant pasture. It is very prevalent.
Traditional names for A. millefolium include arrowroot, bad man's plaything, bloodwort, carpenter's weed, death flower, devil's nettle, eerie, field hops, gearwe, hundred leaved grass, knight's milefoil, knyghten, milefolium, milfoil, millefoil, noble yarrow, nosebleed, old man's mustard, old man's pepper, sanguinary, seven year's love, snake's grass, soldier, soldier's woundwort, stanchweed, thousand seal, woundwort, yarroway, yerw. The English name yarrow comes from the Saxon (Old English) word gearwe, which is related to both the Dutch word gerw and the Old High German word garawa.
Yarrow and its North American varieties were traditionally used by many Native American nations across the continent. The Navajo historically considered it a "life medicine" and chewed the plant for toothaches and used its infusions for earaches. The Miwok in California use the plant as an analgesic and head cold remedy.
Common yarrow is used by Plains Indigenous peoples, such as the Pawnee, who use the stalk for pain relief. The Cherokee drink a tea of common yarrow to reduce fever and aid in restful sleep.
The occidentalis variety is used medicinally by the Zuni people. The blossoms and root are chewed and the juice applied before fire-walking or fire-eating. A poultice of the pulverized plant is mixed with water and applied to burns.
The Ojibwe people historically sprinkled a decoction of yarrow leaves on hot stones and inhaled it to treat headaches, as well as applied decoctions of the root onto skin for its stimulant effect. They also smoked its florets for ceremonial purposes, as well as placed them on coals and inhaled their smoke to break fevers.
In rare cases, yarrow can cause severe allergic skin rashes; prolonged use can increase the skin's photosensitivity. This can be triggered initially when wet skin comes into contact with cut grass and yarrow together.
According to the ASPCA, yarrow is toxic to dogs, cats, and horses, causing increased urination, vomiting, diarrhea and dermatitis.
In a standard rodent model for reproductive toxicity, aqueous extracts of yarrow produced a significant increase in the percentage of abnormal sperm.
Chamazulene and δ-Cadinol are chemical compounds found in A. millefolium. The chromophore of azulene was discovered in yarrow and wormwood and named in 1863 by Septimus Piesse.
Illustration in Koehlers Medizinal-Pflanzen in naturgetreuen Abbildungen und kurz erläuterndem Texte (Franz Eugen Köhler; 1883–1914).
^Shutler D, Campbell AA (2007). "Experimental addition of greenery reduces flea loads in nests of a non-greenery using species, the tree swallow Tachycineta bicolor". Journal of Avian Biology. 38 (1): 7–12. doi:10.1111/j.2007.0908-8857.04015.x.
^Predicting Presence of Proazulenes in the Achillea millefolium Group. Barbara Michler and Carl-Gerold Arnold, Folia Geobotanica, Vol. 34, No. 1, Ecology of Closely Related Plant Species. Proceedings of the 40th Symposium of the International Association of Vegetation Science (1999), pages 143–161 (jstor stable URL)
^Essential oil composition and larvicidal activity of six Mediterranean aromatic plants against the mosquito Aedes albopictus (Diptera: Culicidae) Conti B., Canale A., Bertoli A., Gozzini F., Pistelli L. Parasitology Research 2010 107:6 (1455–1461)
^Dalsenter P, Cavalcanti A, Andrade A, Araújo S, Marques M (2004). "Reproductive evaluation of aqueous crude extract of Achillea millefolium L. (Asteraceae) in Wistar rats". Reprod Toxicol. 18 (6): 819–23. doi:10.1016/j.reprotox.2004.04.011. PMID15279880.