Achillea millefolium
Achillea millefolium or Yarrow (other common names Common Yarrow, Gordaldo, Nosebleed plant, Old Man's Pepper, Sanguinary, Soldier's Woundwort, Thousand-leaf (as its binomial name affirms), Thousand-seal) is a flowering plant in the family Asteraceae, native to the Northern Hemisphere.

# Description
Common Yarrow is an erect herbaceous perennial plant that produces one to several stems (0.2 to 1m tall) and has a 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 4 to 9 phyllaries and contains ray and disk flowers which are white to pink.  There are generally 3 to 8 ray flowers that are ovate to round.  Disk flowers range from 15 to 40.  The inflorescence is produced in a flat-topped cluster.  Yarrow grows up to 3500m above sea level.  The plant commonly flowers from May through June, and is a frequent component in butterfly gardens. Common yarrow is frequently found in the mildly disturbed soil of grasslands and open forests. Active growth occurs in the spring.

# Establishment
Common yarrow is a drought tolerant species of which there are several different ornamental cultivars.  Seeds require light for germination, so optimal germination occurs when planted no deeper than 14 inch.  Seeds also require a temperature of 65-75 degrees Fahrenheit.  Common yarrow responds best to soil that is poorly developed and well drained.  The plant has a relatively short life, but may be prolonged by dividing the plant every other year, and planting 12 to 18 inches apart.  Common yarrow is a weedy species and can become invasive.  It may suffer from mildew or root rot if not planted in well-drained soil.
There are several varieties and subspecies:
- Achillea millefolium subsp. millefolium
Achillea millefolium subsp. millefolium var. millefolium - Europe, Asia
Achillea millefolium subsp. millefolium var. alpicola - Rocky Mountains
Achillea millefolium subsp. millefolium var. borealis - Arctic regions
Achillea millefolium subsp. millefolium var. californica - California
Achillea millefolium subsp. millefolium var. occidentalis - North America
Achillea millefolium subsp. millefolium var. pacifica - west coast of North America
Achillea millefolium subsp. millefolium var. puberula - California
Achillea millefolium subsp. millefolium var. rubra - Southern Appalachians
- Achillea millefolium subsp. millefolium var. millefolium - Europe, Asia
- Achillea millefolium subsp. millefolium var. alpicola - Rocky Mountains
- Achillea millefolium subsp. millefolium var. borealis - Arctic regions
- Achillea millefolium subsp. millefolium var. californica - California
- Achillea millefolium subsp. millefolium var. occidentalis - North America
- Achillea millefolium subsp. millefolium var. pacifica - west coast of North America
- Achillea millefolium subsp. millefolium var. puberula - California
- Achillea millefolium subsp. millefolium var. rubra - Southern Appalachians
- Achillea millefolium subsp. chitralensis - western Himalaya
- Achillea millefolium subsp. sudetica - Alps, Carpathians

# Cultivation and uses
Yarrows can be planted to combat soil erosion due to the plant's resistance to drought.
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 of yarrow 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.
Old folk names for Yarrow include arrowroot, bad man's plaything, 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, stanch weed, thousand seal, woundwort, yarroway, yerw.
The English name Yarrow comes from the Saxon and Dutch words 'Gearwe' and 'Yerw' respectively.
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.

## Herbal medicine
Yarrow has seen historical use as a medicine, mainly because of its astringent effects.  Decoctions have been used to treat inflammations such as piles (hemorrhoids), and also headaches. Confusingly, it has been said to both stop bleeding and promote it.  Infusions of Yarrow, taken either internally or externally, are said to speed recovery from severe bruising.  The most medicinally active part of the plant are 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, and urinary systems.
The flowers, rich in chemicals are converted by steam into anti-allergenic compounds. The flowers are used for various allergic mucus problems, including hay fever. Harvest during summer and autumn. Drink the infused flower for upper respiratory phlegm or use externally as a wash for eczema. Inhale for hay fever and mild asthma, use fresh in boiling water.
The dark blue essential oil, extracted by steam distillation of the flowers, is generally used as an anti-inflammatory or in chest rubs for colds and influenza. Massage oil for inflamed joints, dilute 5-10 drops yarrow oil in 25 ml infused St. John's wort oil. A chest rub can be made for chesty colds and influenza, combine with eucalyptus, peppermint, hyssop, or thyme oils, diluting a total of 20 drops of oil in 25 ml almond or sunflower oil.
The leaves encourage clotting, so it can be used fresh for nosebleeds. However, inserting a leaf in the nostril may also start a nosebleed; this was once done to relieve migraines. Harvest throughout the growing season.
The aerial parts 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. Also useful in menstrual disorders, and as an effective sweating remedy to bring down fevers. Harvest during flowering. The tincture is used for urinary disorders or menstrual problems. Prescribed for cardiovascular complaints. Soak a pad in an infusion or dilute tincture to soothe varicose veins.
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:
Amenorrhea, anti-inflammatory, bowels, bleeding, blood clots, blood pressure (lowers), blood purifier, blood vessels (tones), Catarrh (acute, repertory), colds, chicken pox, circulation, contraceptive (unproven), cystitis, diabetes treatment, digestion (stimulates), dyspepsia, eczema, fevers, flu's, gastritis, glandular system, gum ailments, Heartbeat (slow), influenza, insect repellant, internal bleeding, liver (stimulates and regulates), lungs (hemorrhage), measles, menses (suppressed), menorrhagia, Menstruation (regulates, relieves pain), Nipples (soreness), nosebleeds, piles (bleeding), smallpox, stomach sickness, toothache, thrombosis, ulcers, urinary antiseptic, Uterus (tighten and contract), varicose veins, vision.
The salicylic acid derivatives are a component of aspirin, which may account for its use in treating fevers and reducing pain.  Yarrow tea is also said to be able to clear up a cold within 24 hours.

## Companion planting
Yarrow is considered an especially useful companion plant, not only repelling some bad insects while attracting good, predatory ones, but also improving soil quality. It attracts predatory wasps, which drink the nectar and then use insect pests as food for their larvae. Similarly, it attracts ladybugs and hoverflies. Its leaves are thought to be good fertilizer, and a beneficial addative for compost.
It is also considered directly beneficial to other plants, improving the health of sick plants when grown near them.

# Dangers
In rare cases, yarrow can cause severe allergic skin rashes; prolonged use can increase the skin's photosensitivity.
In one study alcohol extracts of yarrow impaired the sperm production of laboratory rats.

# Trivia
- The most authentic way to cast the I Ching uses dried yarrow stalks. The stems are said to be good for divining the future.
- In China, it is said that it grows around the grave of Confucius.
- Chinese proverbs claim that yarrow brightens the eyes and promotes intelligence.
- In the 1500s, the British herbalist John Gerard recommended it for relieving "swelling of those secret parts."
- Some people believed that you could determine the devotion of a lover by poking a yarrow leaf up your 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).
- Homer tells us that the centaur Chiron, who conveyed herbal secrets to his human pupils, 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.
- Yarrow grows native in the orient. Oriental tradition assured mountain wanderers that where the yarrow grew neither tigers nor wolves nor poisonous plants would be found.
- Nursery rhymes say if you put a yarrow sachet under your pillow, you will dream of your own true love. If you dream of cabbages (the leaves do have a similar scent), then death or other serious misfortune will strike.
- Yarrow 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, devils plaything, and bad man's plaything.
- Western European tradition 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.
- Hang a bunch of dried yarrow or yarrow that had been used in wedding decorations over the bed, to ensure a lasting love for at least seven years.
- Shakers used yarrow for complaints from haemorrhages to flatulence
- Navajo Indians consider it to be a "life medicine", and chewed it for toothaches, and poured an infusion into ears for earaches.
- Several tribes of the Plains region of the United States 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.
- During the excavation of a 40,000-60,000 year old neanderthal tomb, pollen from yarrow (among other herbs) was found.
- It has been used as a Quinine substitute

# Gallery
- File:Achilleamillefolium.jpg
- File:Achillea millefolium.jpg
- File:Mp-Achillea millefolium.jpg
- File:Red Achillea millefolium.jpg