Achillea millefolium L. (Yarrow)

Pronounce the genus name a-KILL' ee-ah or a-KIL-lee-a, and the specific epithet mil-le-FOE-lee-um.

Achillea millefolium L. (Yarrow)

English Common Names

Yarrow, milfoil. The name "yarrow" is said to have originated from Scots Gaelic, where it means "rough stream," and is the name of Scotland's Yarrow River, as well as a place in the county of Selkirkshire. "Yarrow" refers chiefly to A. millefolium, but is also sometimes used for related species. The name milfoil, which refers to the finely dissected foliage, is a corruption of millefolium, meaning thousand-leaved, originally from Latin. Uncommon or archaic names include: band man's plaything, bloodwort, carpenter's weed, devil's nettle, devil's plaything, field hop, nose bleed, old man's pepper, sanguinary, soldier's woundwort, staunchweed, thousand-leaf, thousand weed, and white yarrow.

French Common Names

Achillée millefeuille, herbe à dinde, persil à dinde.

Morphology

Yarrow plants are strongly aromatic, long-lived perennial herbs, 10-100 (typically 30-60) cm tall, with highly dissected leaves to 15 cm long, and flowers in a flat-topped inflorescence. As with most members of the daisy family, what appears to be a single, small flower about 5 mm across, is actually a flower head, often including outer ray flowers and inner disc flowers. The blooms are usually white, with pink, magenta, and red occasionally found. The flowers, appearing in July and August, are self-incompatible and pollinated by insects. The "seeds," actually small, dry indehiscent fruits about 2 mm long, mature in August and September, and are probably (like many other plants apparently lacking special dispersal adaptations) disseminated by adhesion to wet animals, by blowing over snow surfaces, and in other ways. They are not equipped with the parachute-like pappus that enables effective wind dispersal in many members of the daisy family. Yarrow overwinters in cold climates as a dormant rosette. The plant spreads from an extensive, much-branched rhizome system.

Classification and Geography

Achillea millefolium occurs mostly in temperate and boreal zones of the Northern Hemisphere, and to a lesser extent in more southern regions. It is a very variable and widespread species, for which a satisfactory infraspecific classification is not available. Diploid, tetraploid, and hexaploid plants (respectively with 18, 36, and 54 chromosomes) are known.

In Canada the hexaploids occur mainly in the East, and appear to represent weedy plants introduced from Europe. Indigenous Canadian A. millefolium is often segregated into several species. Two such segregates, A. lanulosa Nutt. (= A. millefolium var. lanulosa (Nutt.) Piper) and A. borealis Bong. (= A. millefolium var. borealis (Bong.) Farw.), occur mostly as tetraploid (also as hexaploid) plants across Canada. Unlike the former, the latter variant is mostly absent from the southern prairies and southern Ontario and Quebec, while more frequent in the north, in alpine regions, and along both seacoasts. Neither chromosome number nor morphological features are consistently helpful in distinguishing the major indigenous Canadian variants, which are best simply assigned to A. millefolium sensu lato (i.e., in the broad sense).

As the venerable Harvard botanist M.L. Fernald put it a half century ago, yarrow is still "sadly in need of a well-balanced study, its intricacies not properly understood." One of the more interesting variants that recent studies have supported as distinct is ssp. megacephala (Raup) Argus. It is one of several taxa (including Stellaria arenicola Raup, Deschampsia mackenzieana Raup, and Salix silicicola Raup) that are endemic to the Athabasca sand dunes on the south shore of Lake Athabasca in northwestern Saskatchewan. The distinctive taxa occurring in this region are believed to have evolved recently, during the Holocene (10,000 B.P. to the present).

Distribution Map

Description of this image follows.
Description – Distribution map

Map showing the distribution of Achillea millefolium: mostly in temperate and boreal zones of the Northern Hemisphere, and to a lesser extent in more southern regions.

Ecology

Yarrow occurs in a wide variety of natural habitats, such as tundra meadows, saline flats, salt marshes, sand dunes, edges of woods, rocky outcrops, and cliffs.

This species appears to be Canada's second most common weed (although not really noxious), surpassed only by the dandelion. It is often found as a weed of open areas, such as pastures, meadows, lawns, roadsides, and waste ground. It does not tolerate shade well, but grows very well on poor soils. Yarrow may occur beside lake shores and stream edges, but is quite drought-tolerant. Its ability to withstand dry conditions is due in part to a deep, extensive root system.

Yarrow has been a favourite subject of investigation of students of genecology, who have demonstrated numerous ecotypes, highly specialized to existence in particular habitats. For example genetically-short plants occur in some frequently cut lawns and classic studies of climatic races in plants were based on Achillea.

Medicinal Uses

Yarrow has been used medicinally for millennia in both North America and Europe. Its reputation for healing wounds led to such common names as stanchweed, bloodwort, soldier's woundwort, nosebleed, and carpenter's grass.

Principal traditional uses besides stopping the flow of blood from wounds included treatment of fevers, the common cold, diarrhea, dysentery, and hypertension. Yarrow has also been used in folk medicine as a cure for toothache, earache, and diseases of the lungs, bladder and kidneys.

Today, it is employed internally (as a tea, tincture or pill) to treat gastrointestinal complaints (inflammation, diarrhea, flatulence, cramps), and as a bitter aromatic (to stimulate appetite); and externally in poultices, lotions and bath preparations. Yarrow is present in more than 20 pharmaceutical products marketed in Canada, and is very popular in commercial European herbal remedies.

Toxicity

A reported case of the death of a calf following ingestion of a single plant is often cited, but this is possibly an incorrect interpretation, since the plant does appear to be consumed regularly by grazing animals.

"Yarrow dermatitis" involves itching and inflammatory changes in the skin with the formation of vesicles. This is sometimes accompanied by development of photosensitivity (i.e., the condition is triggered by sunlight). Those with allergies to the Asteraceae (Compositae) family, such as susceptibility to ragweed hay fever, should be on guard for allergic reactions to any type of exposure to yarrow - even simply drinking a herbal tea.

Except for occasional cases of hay fever and dermatitis, yarrow is generally considered non-toxic. Nevertheless, as with most medicinal herbs, large doses and prolonged use are inadvisable and can be dangerous. Yarrow should be avoided during pregnancy, because it may stimulate the uterus. High doses may interfere with anticoagulant and hypo- or hypertensive therapies. Caution has also been recommended for epileptic patients.

Chemistry

Well over a hundred chemicals have been characterized in yarrow. Of greatest interest are the lactones, present in a volatile oil. A metabolic derivative of these, azulene, was once thought to be the constituent primarily responsible for the anti-inflammatory and antipruritic properties of yarrow; however, the medicinal value could be due to chamazulene, the sesquiterpene lactones, or other constituents such as tannins, menthol, camphor, sterols and triterpenes. The antispasmodic activity of yarrow could be due to its flavonoids.

The alkaloid achilleine is an active hemostatic agent, and may explain the traditional uses of checking bleeding of wounds and sores. It has been hypothesized that the salicylic acid derivatives eugenol, menthol, or similar compounds may produce local analgesia and reduction of fever. The presence of thujone, a known abortifacient, might explain some traditional uses of yarrow associated with the female reproductive system (however, thujone is usually present only in limited amounts).

There is evidence of taxonomic and geographical differences in content of these chemicals, but documentation with herbarium vouchers has been poor, and considerable additional analysis is needed. The important constituent chamazule appears to be present in tetraploid plants only. Some have claimed that American plants are more effective medicinally than European plants.

Non-Medicinal Uses

Yarrow is a very popular ornamental plant, and there are numerous attractive cultivars (many of which are hybrids) with deeply coloured flowers. In some areas, it is recommended as a groundcover to control soil erosion on slopes and hillsides. Its capacity to spread by rhizomes makes it valuable for this application. It is ironic that yarrow is also recommended as a low-maintenance, infrequently mowed lawn, as vigorous attempts are often made to eliminate it from lawns, where low-growing ecotypes are capable of blooming under the lawn mower blades. Yarrow is widely used for dried and fresh flower arrangements, valued for the feathery, fernlike foliage and pungency.

Despite its bitter taste, some domestic livestock (notably sheep) and deer consume yarrow. The French name herbe à dinde reflects previous use of the plant as chicken feed. Cows grazing on yarrow may produce dairy products with an undesirable flavour, but cattle seem to avoid it. Young yarrow leaves are sometimes consumed (cooked or fresh) in salads (large amounts are said to turn urine brown). The leaves and flowers are used to flavour liqueurs, and were once substituted for hops to flavour beer.

In addition to food and ornamental usage, yarrow has been employed as a tobacco, snuff, and hair rinse reputed to brighten blonde hair. Yarrow also has insecticidal constituents, and this is consistent with its reputation as an insect-repelling garden plant that dissuades visits from some ants, flies, and beetles.

Agricultural and Commercial Aspects

Most commercial supplies of medicinal yarrow are obtained from Europe. Yarrow is considered to be a minor essential oil crop, but nevertheless the annual world production of oil is substantial - about 800 tonnes, estimated to have a value of (US$) 88 million.

Features of yarrow make it easy to adapt as a crop. Germination percentages are generally high, and the seeds only need to be scattered on the soil surface. Seeds sown in the autumn germinate in spring, produce sturdy rosettes the first year and reach mature flowering size in the second year. Since they are perennial, the plants grow back after harvesting of above-ground parts. An additional potential benefit is that some populations yield sufficient nectar for honey production. With its capability for regional adaptation and ability to grow in poor soils of various moisture regimes, Yarrow is a relatively undemanding crop that can be grown throughout much of Canada. Effective selection of cultivars will require careful attention to genotypic variation, especially with regard to chemical composition.

Myths, Legends, Tales, Folklore, and Interesting Facts

  • The generic name Achillea is usually interpreted as a reference to Achilles, the legendary Greek hero of the Trojan War (about 1200 B.C.) as reported in Homer's epic poem, Iliad. He is said to have used the foliage of yarrow to stanch the flow of blood from wounded fellow soldiers. Achilles, the mortal son of Thetis, was dipped by his heel into a sacred fire to burn away his mortality. Unfortunately his heel, not bathed in the fire, remained vulnerable to injury. Subsequently he was struck in the heel by an arrow, which killed him, thereafter providing a metaphor for an area of weakness in something that is otherwise invulnerable. A less romantic interpretation of the genus name is that it commemorates a Greek doctor named Achilles who recorded the medicinal uses of the plant.
  • Ancient Chinese sages are said to have selected yarrow stalks at random as a means of consulting the oracles of the I Ching (Book of Changes; a compendium alleged to contain the wisdom of thousands of years of human history).
  • Yarrow was once used in Ireland for love divination: young girls would cultivate a yarrow plant and subsequently place it beneath their pillow so that they would dream of their sweetheart. It was brought by bridesmaids to weddings to ensure seven years of love. The closest that research has come to supporting such uses is the finding that the volatile oil of yarrow causes a sexual response in male cockroaches.
  • In France and Ireland yarrow is one of the herbs of St. John (John the Baptist, Christian martyr born on June 24), and on St. John's Eve (June 23, time of traditional European midsummer celebration) the Irish hang it in their houses to avert illness.
  • Unearthed fossil pollen from ancient burial caves has been interpreted as evidence of prehistoric use of the herb.

Selected References

  • Armitage, A.M. 1992. Field studies of Achillea as a cut flower: longevity, spacing, and cultivar response. J. Am. Soc. Hortic. Sci. 117: 65-67.

  • Bélanger, A., and Dextraze, L. 1992. Variability of chamazulene within Achillea millefolium. Acta Hortic. 330: 141-146.

  • Bélanger, A., and Dextraze, L. 1993. Variation intraspécifique de la composition chimique de l'huile essentielle d'Achillée millefeuille. Rivista Italiana, EPPOS 4: 708-712.

  • Bélanger, A., Dextraze, L., Lachance, Y., and Savard, S. 1991. Extraction et caractérisation de l'achillée millefeuille (Achillea millefolium L.) cultivé au Québec. Rivista Italiana, EPPOS 2: 574-580.

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

  • Bugge, G. 1991. Investigation on the content of azulene and the chromosome number of the taxa of the Achillea millefolium complex. Angew. Bot. 65: 331-339. [In German.]

  • Chandler, R.F., Hooper, S.N., and Harvey, M.J. 1982. Ethnobotany and phytochemistry of yarrow, Achillea millefolium, Compositae. Econ. Bot. 36: 203-232.

  • Chandler, R.F., Hooper, S.N., Hooper, D.L., Jamieson, W.D., Flinn, C.G., and Safe, L.M. 1991. Herbal remedies of the Maritime Indians: sterols and triterpenes of Achillea millefolium L. (yarrow). J. Ethnopharmacol. 33: 187-191.

  • Clausen, J., Hiesey, W.M., and Nobs, M. 1955. Diploid, tetraploid and hexaploid hybrids of Achillea. Carnegie Inst. Wash. Year Book 54: 182-183.

  • Clausen, J., Keck, D.D., and Hiesey, W.M. 1940. Experimental studies on the nature of species. I. The effect of varied environments on western North American plants. Carnegie Inst. Wash. Publ. 520: 296-324.

  • Clausen, J., Keck, D.D., and Hiesey, W.M. 1948. Experimental studies on the nature of species. III. Environmental responses of climatic races of Achillea. Carnegie Inst. Wash. Publ. 581: 1-129.

  • Connelly, K. 1991. A yarrow lawn. Pac. Hortic. (San Francisco) 52(3): 28-30.

  • Davies, M.G., and Kersey, P.J. 1986. Contact allergy to yarrow and dandelion. Contact Dermatitis 14: 256-257.

  • Falk, A.J.C., Bauer, L., and Bell, C.L. 1974. The constituents of the essential oil from Achillea millefolium L. Lloydia 37: 598-602.

  • Field, R.J., and Jayaweera, C.S. 1985. Regeneration of yarrow (Achillea millefolium) rhizomes as influenced by rhizome age, fragmentation and depth of soil burial. Plant Protect. Q. 1: 71-73.

  • Figueiredo, A.C., and Pais, M.S.S. 1994. Ultrastructural aspects of the glandular cells from the secretory trichomes and from the cell suspension cultures of Achillea millefolium L. ssp. millefolium. Ann. Bot. 74: 179-190.

  • Figueiredo, A.C., Barroso, J.G., Pais, M.S.S., and Scheffer, J.J.C. 1992. Composition of the essential oils from leaves and flowers of Achillea millefolium ssp. millefolium. Flavour Fragrance J. 7: 219-222.

  • Gervais, C. 1977. Cytological investigation of the Achillea millefolium complex (Compositae) in Quebec. Can. J. Bot. 55: 796-808.

  • Goldberg, A.S., Mueller, E.C., Eigen,E., and Desalva, S.J. 1969. Isolation of the anti-inflammatory principles from Achillea millefolium (Compositae). J. Pharm. Sci. 58: 938-941.

  • Guedon, D., Abbe, P., and Lamaison, J.L. 1993. Leaf and flower head flavonoids of Achillea millefolium L. subspecies. Biochem. Syst. Ecol. 21: 607-611.

  • Gurevitch, J. 1988. Variation in leaf dissection and leaf energy budgets among populations of Achillea from an altitudinal gradient. Am. J. Bot. 75: 1298-1306

  • Hausen, B.M., Breuer, J., Weglewski, J., and Rucker, G. 1991. Alpha-Peroxyachifolid and other new sensitizing sesquiterpene lactones from yarrow (Achillea millefolium L., Compositae). Contact Dermatitis 24: 274-280.

  • Hiesey, W.M. 1953. Comparative growth between and within climatic races of Achillea under controlled conditions. Evolution 7: 297-316.

  • Hiesey, W.M., and Nobs, M. 1970. Genetic and transplant studies on contrasting species and ecological races of the Achillea millefolium complex. Bot. Gaz. 131: 245-259.

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

  • Hofmann, L., and Fritz, D. 1993. Genetical, ontogenetical and environmental caused variability of the essential oil of different types of the Achillea millefolium 'complex.' Acta Hortic. 330: 147-157.

  • Kokkalou, E., Kokkini, S., and Hanlidou, E. 1992. Volatile constituents of Achillea millefolium in relation to their infraspecific variation. Biochem. Syst. Ecol. 20: 665-670.

  • Krupinska, A.A. 1986. Distribution of azulene-containing and azulene-free forms of yarrow (Achillea millefolium) sensu lato in northwestern Poland. Herba Pol. 31: 39-46. [In Polish.]

  • Lamaison, J.L., and Carnat, A.P. 1988. Study of azulene in three subspecies of Achillea millefolium L. Ann. Pharm. Fr. 46(2): 139-143. [In French.]

  • Lawrence, B.M. 1984. Progress in essential oils. Perfum. Flavorist 9(4): 37-41, 43, 46-48.

  • Lawrence, W.E. 1947. Chromosome numbers in Achillea in relation to geographical distribution. Am. J. Bot. 34: 538-545.

  • Michler, B., Preitschopf, A., Erhard, P., and Arnold, C.G. 1992. Achillea millefolium: relationships among habitat factors, ploidy, occurrence of proazulene and the content of chamazulene in the essential oil. Pz (Pharmazeutische Zeitung) Wissenschaft 137: 23-29. [In German.]

  • Mittich, L.W. 1990. Yarrow - the herb of Achilles. Weed Technol. 4: 451-453.

  • Mulligan, G.A., and Bassett, I.J. 1959. Achillea millefolium complex in Canada and portions of the United States. Can. J. Bot. 37: 73-79.

  • Pireh, W., and Tyrl, R.J. 1980. Cytogeography of Achillea millefolium in Oklahoma and adjacent states. Rhodora 82: 361-367.

  • Purdy, B.G., and Bayer, R.J. 1996. Genetic variation in populations of the endemic Achillea millefolium ssp. megacephala from the Athabasca sand dunes and the widespread ssp. lanulosa in western North America. Can. J. Bot. 74: 1138-1146.

  • Robocker, W.C. 1977. Germination of the seeds of common yarrow, Achilea millefolium and its herbicidal control. Weed Sci. 25: 456-459.

  • Saukel, J., and Laenger, R. 1992. The Achillea millefolium -- group (Asteraceae) in central Europe. 1. Introduction, evaluation of characters and plant material. Phyton Ann. Rei. Bot. Horn. 31: 185-207. [In German.]

  • Saukel, J., and Laenger, R. 1992. The Achillea millefolium -- group (Asteraceae) in central Europe: 2. Comparison of populations, multivariate classification and biosystematic comments. Phyton Ann. Rei. Bot. Horn. 32: 47-78. [In German.]

  • Scheffer, M.C., Ronzelli, P., and Koehler, H.S. 1993. Influence of organic fertilization on the biomass, yield and composition of the essential oil of Achillea millefolium L. Acta Hortic. 331: 109-114.

  • Schneider, A. 1984. Our honey flora: Achillea millefolium L. [Taxonomic description]. Unsere Bienenflora: die gemeine Schafgarbe Achillea millefolium L.). Allg. Dtsch. Imkerztg. 18: 323. [In German.]

  • Stahl, E., and Wollensah, A. 1986. Observations on the function of the glandular hairs of yarrow. Effects of selective herbicides on the glandular hairs and tissue of the florets. J. Plant Physiol. 122: 93-96.

  • Terziiski, D., Yurukova-Grancharova, P., Daskalova, T., and Robeva, P. 1995. Apomixis in the morphological complex of Achillea millefolium (Asteraceae). Dokl. Bulgarskata Akad. Nauk. 48(3): 53-56.

  • Tewari, J.P., Srivastava, M.C., and Bajpai, J.L. 1974. Phytopharmacologic studies of Achillea millefolium Linn. Indian J. Med. Sci. 28: 331-336.

  • Tunon, H., Thorsell, W., and Bohlin, L. 1994. Mosquito repelling activity of compounds occurring in Achillea millefolium L. (Asteraceae). Econ. Bot. 48: 111-120.

  • Tozyo, T., Yoshimura, Y., Sakurai, K., Uchida, N., Takeda, Y., Nakai, H., and Ishii, H. 1994. Novel antitumor sesquiterpenoids in Achillea millefolium. Chem. Pharm. Bull. (Tokyo). 42: 1096-1100.

  • Tyrl, R.J. 1975. Origin and distribution of polyploid Achillea [millefolium] (Compositae) in western North America. Brittonia 27: 187-196.

  • Ustyuzhanin, A.A., Konovalov, D.A, Shreter, A.I., Konovalova, O.A., and Rybalko, K.S. 1987. Chamazulene content in Achillea millefolium L. sensu lato in the European part of the USSR. Rastit. Resur. 23: 424-429 [In Russian.]

  • Valant-Vetschera, A.K.M., and Wollenweber, E. 1988. Leaf flavonoids of the Achillea millefolium group: Part II. Distribution patterns of free aglycones in leaf exudates. J. Biochem. Syst. Ecol. 16: 605-614.

  • Wallner, E., Weising, K., Rompf, R., Kahl, G., and Kopp, B. 1996. Oligonucleotide fingerprinting and RAPD analysis of Achillea species: characterization and long-term monitoring of micropropagated clones. Plant Cell Rep. 15: 647-652.

  • Warwick, S.I., and Black, L. 1982. The biology of Canadian weeds. 52. Achillea millefolium L. s.l. Can. J. Plant Sci. 62: 163-182.

  • Warwick, S.I., and Briggs, D. 1979. The genecology of lawn weeds. III. Cultivation experiments with Achillea millefolium L., Bellis perennis L., Plantago lanceolata L., Plantago major L., and Prunella vulgaris L. collected from lawns and contrasting grassland habitats. New Phytol. 83: 509-536.

  • Warwick, S.I., and Briggs, D. 1980. The genecology of lawn weeds. Vi. The adaptive significance of variation in Achillea millefolium L. as investigated by transplant experiments. New Phytol. 85: 451-460.