Achillea millefolium, known commonly 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.^[1] 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 staunching the flow of blood from wounds.^[2] 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.^[3]

Description[edit]

Achillea millefolium is an erect herbaceousperennial plant that produces one to several stems 0.2–1 metre (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 long, bipinnate or tripinnate, almost feathery, and arranged spirally on the stems. The leaves are cauline, and more or less clasping.^[3]

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 cluster. The fruits are small achenes.^[3]

The plant has a strong, sweet scent, similar to chrysanthemums.^[1]

Distribution[edit]

Yarrow grows from sea level to 3,500 metres (11,500 ft) in elevation. The plant commonly flowers from May through June. Common yarrow is frequently found in the mildly disturbed soil of grasslands and open forests. Active growth occurs in the spring.^[1][3]

In North America, both native and introduced genotypes, and both diploid and polyploid plants are found.^[4] It is found in every habitat throughout California except the Colorado and Mojave Deserts.^[5][6] common yarrow produces an average yield of 43,000 plants per acre, with a total dry weight of 10,500 lbs.^[7]

Varieties[edit]

The several varieties and subspecies include:

• Achillea millefolium subsp. millefolium

A. m. subsp. m. var. millefolium - Europe, Asia

A. m. subsp. m. var. borealis - Arctic regions

A. m. subsp. m. var. rubra - Southern Appalachians

A. millefolium subsp. chitralensis - western Himalaya

A. millefolium subsp. sudetica - Alps, Carpathians

Achillea millefolium var. alpicola — Western United States, Alaska^[8]

Achillea millefolium var. californica — California, Pacific Northwest^[9][10][11]

Achillea millefolium var. occidentalis — North America^[12]

Achillea millefolium var. pacifica — west coast of North America, Alaska^[13]

Achillea millefolium var. puberula — endemic to California^[14]

Uses[edit]

Cultivation[edit]

Achillea millefolium is cultivated as an ornamental plant by many plant nurseries. It is planted in gardens and natural landscaping settings of diverse climates and styles. They include native plant, drought-tolerant, and wildlife gardens. The plant is a frequent component of butterfly gardens. The plant prefers well-drained soil in full sun, but can be grown in less ideal conditions.^[15][16][17]

Propagation[edit]

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° (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 12–18 in (30–46 cm) apart. It can become invasive.^[18]

Cultivars[edit]

The species use in traditional gardens has generally been superseded by cultivars with specific 'improved' qualities.^[19] Some are used as drought tolerant lawn replacements, with periodic mowing.^[20] The many different ornamental cultivars include: 'Paprika',^[21] 'Cerise Queen', 'Red Beauty',^[22] 'Red Velvet',^[23] 'Saucy Seduction', 'Strawberry Seduction' (red), 'Island Pink' (pink),^[24] and 'Calistoga' (white),^[25] and 'Sonoma Coast' (white).^[26] Several, including 'Kelwayi',^[27] and 'Lansdorferglut' (both pink)^[28] 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,^[29] including: 'Appleblossom', 'Fanal', 'Hoffnung', and 'Moonshine'.^[30]

Companion planting[edit]

Yarrow, Achillea millefolium, is considered an especially useful companion plant, repelling some insect pests while attracting good, predatory ones. It attracts predatory wasps, which drink the nectar and then use insect pests as food for their larvae. Similarly, it attracts ladybirds and hoverflies.^[17]

Agriculture[edit]

Achillea 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.

Herbal and traditional uses[edit]

The herb is purported to be a diaphoretic, astringent,^[31]tonic,^[31]stimulant and mild aromatic. It contains isovaleric acid, salicylic acid, asparagin, sterols, flavonoids, bitters, tannins, and coumarins. The plant also has a long history as a powerful 'healing herb' used topically for wounds, cuts and abrasions. The genus name Achillea is derived from mythical Greek character, Achilles,^[31] who reportedly carried it with his army to treat battle wounds. This medicinal action is also reflected in some of the common names mentioned below, such as staunchweed and soldier's woundwort.^[1]

The stalks are dried and used as a randomising agent in I Ching divination.^[32]

In the Middle Ages, yarrow was part of a herbal mixture known as gruit used in the flavouring of beer prior to the use of hops.^{[citation needed]} The flowers and leaves are used in making some liquors and bitters.^[1]

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.^[33]

Yarrow has also been used as a food, and was very popular as a vegetable in the 17th century. The younger leaves are said to be a pleasant leaf vegetable when cooked like spinach, or in a soup. Yarrow is sweet with a slight bitter taste. The leaves can also be dried and used as a herb in cooking.

A. millefolium has seen historical use as a medicine, often because of its astringent effects.^[1]

The dark blue essential oil, extracted by steam distillation of the flowers, is generally used as an anti-inflammatory^[34] or in chest rubs for colds and influenza.^[35]

The leaves encourage clotting, so it can be used fresh for nosebleeds.^[36] The aerial parts of the plant are used for phlegm conditions, as a bitter digestive tonic to encourage bile flow, and as a diuretic.^[37] The aerial parts act as a tonic for the blood, stimulate the circulation, and can be used for high blood pressure; it is also useful in menstrual disorders, and as an effective sweating remedy to bring down fevers.^[1]

Yarrow intensifies the medicinal action of other herbs taken with it.^[38] It is reported^[39] to be associated with the treatment of the following ailments:

Pain,^[40] antiphlogistic,^[41][42]bleeding, gastrointestinal disorders,^[41] choleretic^[43] inflammation,^[44] emmenagogue,^[45] stomachache.^[46]

Chinese proverbs claim yarrow brightens the eyes and promotes intelligence. Yarrow and tortoiseshell are considered to be lucky in Chinese tradition.^[47]

In classical Greece, Homer tells of the centaur Chiron, who conveyed herbal secrets to his human pupils, and taught Achilles to use yarrow on the battle grounds of Troy.^[48]

Native American uses[edit]

Yarrow, Achillea millefolium and its North American varieties, was used in traditional Native American herbal medicine by tribes across the continent.^[49] The Navajo considered it to be a "life medicine", chewed it for toothaches, and poured an infusion into ears for earaches. The Miwok in California used the plant as an analgesic and head cold remedy.^[49]

Several tribes of the Plains Indians used common yarrow. The Pawnee used the stalk for pain relief. The Chippewa used the leaves for headaches by inhaling it in a steam. They also chewed the roots and applied the saliva to their appendages as a stimulant. The Cherokee drank a tea of common yarrow to reduce fever and aid in restful sleep.^[49]

Among the Zuni people use the occidentalis variety medicinally. 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.^[50] Recently it was reported that treatment with Achillea millefolium may attenuate disease severity, inflammatory responses, and demyelinating lesions in a mouse model of Multiple Sclerosis.^[51]

Dangers[edit]

In rare cases, yarrow can cause severe allergic skin rashes; prolonged use can increase the skin's photosensitivity.^[52] This can be triggered initially when wet skin comes into contact with cut grass and yarrow together.

In one study, aqueous extracts of yarrow impaired the sperm production of laboratory rats.^[53]

Birds[edit]

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.^[54]

Its essential oil kills the larvae of the mosquito Aedes albopictus.^[55]

Similar plants[edit]

Similar species

Other Achillea species have similar foliage and flowers, including: Achillea ageratifolia and Achillea nobilis.

Similar genera

Other plants with white flowers in large compound umbels may be confused with Achillea millefolium, these include: water parsnip—Sium suave (swamp parsnip); western water hemlock—Cicuta douglasii (poison hemlock); and spotted water hemlock—Cicuta maculata (spotted parsley, spotted cowbane). Water parsnip and water hemlock have clusters of small white flowers that are shaped like umbrellas, and both grow in moist soils. Water parsnip leaves are once compound, and water hemlock leaves are three times compound. Water hemlock has a large swelling at the stem base. All parts of water hemlock are highly poisonous.^[56]

Gallery[edit]

• 

  Illustration in Koehlers Medizinal-Pflanzen in naturgetreuen Abbildungen und kurz erläuterndem Texte (Franz Eugen Köhler; 1883–1914).
• 

  Achillea millefolium at BioTrek, California State Polytechnic University, Pomona.
• 

  Achillea millefolium — flower closeup.
• 

  Achenes

• 

  Field of Yarrow in Russia.

See also[edit]

• List of companion plants
• Sacred herbs

References[edit]

Further reading[edit]

• Blanchan, Neltje (2005). Wild Flowers Worth Knowing. Project Gutenberg Literary Archive Foundation. 
• Wood, John (2006). Hardy Perennials and Old Fashioned Flowers. Project Gutenberg Literary Archive Foundation. 
• Hickman, James C., ed. (1993). The Jepson Manual: Higher plants of California. Berkeley, Los Angeles, and London: University of California Press.