thumb|Achillea sp.
thumb|Achillea sp. in a heart shaped form
Achillea millefolium, commonly known as yarrow () or common yarrow, is a flowering plant in the family Asteraceae. Growing to tall, it is characterized by small whitish flowers, a tall stem of fernlike leaves, and a pungent odor.
The plant is native to temperate regions of Eurasia and North America. It has been introduced as feed for livestock in New Zealand and Australia. It has some potential uses, including in traditional medicine.
Description
thumb|[[Petiole (botany)|Petiolate leaves on lower stems]]
thumb|Illustration from [[Köhler's Medicinal Plants (1887–1898)]]
Achillea millefolium is an erect, herbaceous, perennial plant that produces one to several stems in height, and has a spreading rhizomatous growth form. Cauline and more or less clasping, the leaves appear spirally and evenly along the stem, with the largest and most petiolate towards the base; they are long and fernlike, divided bipinnately or tripinnately.
The inflorescence has 4 to 9 phyllaries and contains ray and disk flowers which are white to pink, blooming from March to October. There are generally 3 to 8 ray flowers, which are long The small achene-like fruits are called cypsela. and may be irritating to some.
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.
Yarrow contains isovaleric acid, salicylic acid, asparagine, sterols, and flavonoids. It also contains phenolic acids such as gallic acid, 3, 4-dihydroxy benzoic acid, chlorogenic acid, vanillic acid, caffeic acid, syringic acid, acid, sinapic acid, ferulic acid, cinnamic acid and flavonoid such as myricetin, hesperidin, quercetin, luteolin, kaempferol, apigenin, rutin, hyperoside.
Taxonomy
Subdivision
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
- 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
Etymology
The genus name is derived from mythical Greek character Achilles who, by legend, carried it with his army to treat battle wounds. The specific epithet comes from the featherlike leaves which are minutely divided. It is found in every habitat throughout California except the Colorado and Mojave Deserts. Common yarrow produces an average yield of , with a total dry weight of .
It has been introduced as a feed for livestock in New Zealand and Australia, where it is a common weed of both wet and dry areas, such as roadsides, meadows, fields and coastal places.
Achillea millefolium is a food source for many species of insects, including the larvae of a number of moths, although is not particularly attractive to ladybirds.
Aceria kiefferi <small>(Nalepa, 1891)</small> is a mite that causes galls on A. millefolium.
Cultivation
thumb|A. millefolium 'Paprika' [[cultivar]]
thumb|A. millefolium cultivar
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.
Propagation
For propagation, seeds require light for germination, so optimal germination occurs when planted no deeper than . Seeds also require a germination temperature of . It has a relatively short life in some situations, but may be prolonged by division in the spring every other year, and planting apart. It can become invasive.
Cultivars
The species use in traditional gardens has generally been superseded by cultivars with specific 'improved' qualities. Some are used as drought-tolerant lawns, with periodic mowing. The many different ornamental cultivars include: 'Paprika', 'Cerise Queen', 'Red Beauty', 'Red Velvet', 'Saucy Seduction', 'Strawberry Seduction' (red), 'Island Pink' (pink), 'Calistoga' (white), and 'Sonoma Coast' (white). The following are recipients of the Royal Horticultural Society's Award of Garden Merit:
- 'Credo'
- 'Lachsschönheit' (Galaxy Series)
- 'Martina'
- 'Lansdorferglut'
The many hybrids of this species designated Achillea × taygetea are useful garden subjects, including: 'Appleblossom', 'Fanal', 'Hoffnung', and 'Moonshine'.
Toxicity
Yarrow can cause allergic skin rashes.
According to the American Society for the Prevention of Cruelty to Animals, yarrow is toxic to dogs, cats, and horses, causing increased urination, vomiting, diarrhea and dermatitis. When consumed by cows, an unfavorable flavor is given to their milk.
Uses
thumb|upright|Essential oil
thumb|Yarrow can produce a dense mat of soft leaves.
Traditional medicine
A. millefolium was used in traditional medicine, in part due to its astringent properties and the mild laxative effect of its leaves. It was used in ancient times to heal wounds and stop bleeding, and in the 16th century, the crushed leaves were used to stop nosebleeds.
North American varieties were traditionally used by many Native American nations. The Navajo considered it a "life medicine" and chewed the plant for toothaches and used its infusions for earaches. The Miwok in California used the plant as an analgesic and head cold remedy. Yarrow was used by Plains indigenous peoples to reduce pain or fever and aid sleep. or applied decoctions of the root onto skin for its stimulating effect.
Food
The entire plant is reportedly edible and nutritious, but it is advised not to consume much. The foliage is pungent; both its leaves and flowers are bitter and astringent.
In the Middle Ages, yarrow was part of a herbal mixture known as gruit used in the flavoring of beer prior to the use of hops. However, medieval Dutch and German city accounts from the gruit area do not mention yarrow. It is noted by the Swedish biologist Linnaeus that the Dalecarnians infused the herb in beer. The flowers and leaves are still used in making some liquors and bitters. and repelling some pests.
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 and pasture contained A. millefolium at a density of about 0.3 kg/ha. One factor for its use in grass mixtures was its deep roots, with leaves rich in minerals, minimizing mineral deficiencies in ruminant feed. It was introduced into New Zealand as a drought-tolerant pasture.
Culture
Yarrow has been found with Neanderthal burials, suggesting its association with human species dates to at least 60,000 years ago.
Dried yarrow stalks are used in I Ching divination.
Western world
In antiquity, the plant was known as herba militaris for its use in stanching the flow of blood from wounds. In the Classical Greek epic Iliad, Homer tells of the centaur Chiron, who conveyed herbal secrets to his human pupils and taught Achilles to use yarrow on the battlegrounds of Troy. The genus name Achillea is inspired by the alleged use of the herb by Achilles to treat his soldiers' wounds.
The English name yarrow comes from its Saxon (Old English) name gearwe, which is related to both the Dutch word gerw (alternately yerw) In the eastern counties it may be called yarroway. In the witchcraft trial of Elspeth Reoch in March 1616, she was alleged to have plucked "melefour", thought to be another name for yarrow, and said "In nomine Patris, Fiili, et Spiritus Sancti" to become able to cure distemper (disorders of the four humours) and impart the faculty of prediction. in which Jesus uses the plant to heal his adoptive father. For this reason, in France, it was called herbe de St. Joseph, and it has also been called carpenter's weed in this regard.