Horticulture/Achillea millefolium

Achillea millefolium or Yarrow (other common names Common Yarrow, Gordaldo, Nosebleed plant, Old Man's Pepper, Sanguinary, Milfoil, 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.

Growing Conditions
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 ¼ 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.

Varieties
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. chitralensis - western Himalaya
 * Achillea millefolium subsp. sudetica - Alps, Carpathians

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.

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 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, flus, gastritis, glandular system, gum ailments, Heartbeat (slow), influenza, insect repellent, 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 additive for compost.

It is also considered directly beneficial to other plants, improving the health of sick plants when grown near them.