Achillea millefolium, known commonly as yarrow (pron.: // or common yarrow, is a flowering plant in the family Asteraceae. It is native to temperate regions of the Northern Hemisphere in Asia, Europe, and North America. 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. 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. 
Achillea millefolium is an erect herbaceous perennial plant that produces one to several stems 0.2–1 metre (0.66–3.3 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. 
The inflorescence has four to 9 phyllaries and contains ray and disk flowers which are white to pink. The generally three to eight 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. 
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. 
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.  
- 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 
- Achillea millefolium var. californica — California, Pacific Northwest   
- Achillea millefolium var. occidentalis — North America 
- Achillea millefolium var. pacifica — west coast of North America, Alaska 
- Achillea millefolium var. puberula — endemic to California 
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.   
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.
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',  'Calistoga',  'Cerise Queen', 'Island Pink',  and 'Red Beauty'. and 'Sonoma Coast'.  Several, including 'Kelwayi', and 'Lansdorferglut' have gained the Royal Horticultural Society's Award of Garden Merit.
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 ladybugs and hoverflies. 
It is also planted for improving soil quality. Its leaves are thought to be good fertilizer, and a beneficial additive for compost.
It is also considered directly beneficial to other plants, improving the health of sick plants when grown near them.
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
|This section needs more medical references for verification or relies too heavily on primary sources. (September 2012)|
The herb is purported to be a diaphoretic, astringent, tonic, 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, 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.
The stalks are dried and used as a randomising agent in I Ching divination.
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. The flowers and leaves are used in making some liquors and bitters.
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. and 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 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 as 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. Decoctions have been used to treat inflammations, such as hemorrhoids, and headaches. Confusingly, it has been said to both stop bleeding and promote it. (Depending on the form it is administered, it can do both, which is why when dabbling in using herbs for medicine it is proper to contact a herbalist or other expert. A. millefolium has been used with great success in promoting blood flow, as well as staunching blood flow when properly used.) Infusions of yarrow, taken either internally or externally, are said[by whom?] to speed recovery from severe bruising. The most medicinally active part of the plant is the flowering tops. They also have a mild stimulant effect, and have been used as a snuff. Today, yarrow is valued mainly for its action in colds and influenza, and also for its effect on the circulatory, digestive, excretory, and urinary systems. In the 19th century, yarrow was said to have a greater number of indications than any other herb.
Possible antiallergenic compounds can be extracted from the flowers by steam distillation. The flowers are used to treat various allergic mucus problems, including hay fever. Flowers used in this way are harvested in summer or autumn, and an infusion drunk for upper respiratory phlegm or used externally as a wash for eczema.
The leaves encourage clotting, so it can be used fresh for nosebleeds. The aerial parts of the plant are used for phlegm conditions, as a bitter digestive tonic to encourage bile flow, and as a diuretic. 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.
Yarrow intensifies the medicinal action of other herbs taken with it, and helps eliminate toxins from the body. It is reported to be associated with the treatment of the following ailments:
Pain, amenorrhea, antiphlogistic, bleeding, blood clots, blood pressure (lowers), blood purifier, blood vessels (tones), catarrh (acute, repertory), colds, chicken pox, circulation, contraceptive (unproven), cystitis, diabetes, digestion (stimulates), gastrointestinal disorders, choleretic  dyspepsia, eczema, fevers, flu, gastritis, gum ailments, heartbeat (slow), influenza, inflammation, emmenagogue, internal bleeding, liver (stimulates and regulates), lungs (hemorrhage), measles, menses (suppressed), menorrhagia, menstruation (regulates, relieves pain), nipple soreness, nosebleeds, piles (bleeding), smallpox, stomach sickness, toothache, thrombosis, ulcers, urinary antiseptic, uterus (tighten and contract), stomachache, and varicose veins.
Native American uses
Yarrow, Achillea millefolium and its North American varieties, was used in traditional Native American herbal medicine by tribes across the continent.  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. 
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. 
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.
In one study, aqueous extracts of yarrow impaired the sperm production of laboratory rats.
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 adding yarrow to nests inhibits the growth of parasites.
In popular culture
Stories about yarrow feature in traditional Chinese culture. For example, it is said to grow around the grave of Confucius. Also, the most authentic way to cast the Yi Jing is to use dried yarrow stalks. The stems are said to be good for divining the future.
Chinese proverbs claim yarrow brightens the eyes and promotes intelligence. Yarrow and tortoiseshell are considered to be lucky in Chinese tradition. Oriental tradition also assured mountain wanderers that where the yarrow grew, neither tigers or wolves nor poisonous plants would be found.
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. Achilles is said to have used it to stop the bleeding wounds of his soldiers. For centuries, it has been carried in battle because of its magical, as well as medicinal, properties. Western European tradition also connects yarrow with a goddess and a demon. Yarrow was a witching herb, used to summon the devil or drive him away, but it was also a loving herb in the domain of Aphrodite.
Yarrow also featured in British folk customs and beliefs. It was one of the herbs put in Saxon amulets. These amulets were for protection from everything from blindness to barking dogs. In the Middle Ages, witches were said to use yarrow to make incantations. This may be the source for the common names devil's nettle, devil's plaything, and bad man's plaything. Some people believed one could determine the devotion of a lover by poking a yarrow leaf up one's nostril and twitching the leaf while saying, "Yarroway, yarroway, bear a white blow: if my love loves me, my nose will bleed now". (Yarrow is a nasal irritant, and generally causes the nose to bleed if inserted.)
Nursery rhymes say a yarrow sachet under one's pillow will cause dreams of one's own true love. Dreaming of cabbages (the leaves do have a similar scent) will allow death or other serious misfortune to strike. A folk belief states a bunch of dried yarrow used in wedding decorations hung over the bed will ensure a lasting love for at least seven years.
In literature, in the book The Glass Bead Game by Hermann Hesse, Elder Brother uses yarrow stalks to divine the will of the Oracle.
- Similar species
- 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.
Illustration in Koehlers Medizinal-Pflanzen in naturgetreuen Abbildungen und kurz erläuterndem Texte (Franz Eugen Köhler; 1883-1914).
Achillea millefolium — flower closeup.
Field of Yarrow in Russia.
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