Yarrow, a perennial plant that grows in temperate regions throughout the world, has a long history as a medicinal herb. According to legend, the plant was used by Greek warrior Achilles to staunch the wounds of his soldiers, leading to the plant's scientific name; Achillea millefolium. Modern herbalists still use yarrow for its purported healing properties.
Yarrow belongs to the aster family, making it a close relative of chrysanthemums. It grows upright on a hairy stem and rarely reaches more than 3 feet high. The plant prefers full sun and a warm climate and produces white, pink or purple flowers in summer. Frequently found in fields and roadsides or disturbed areas, yarrow spreads rapidly. Germination takes about 20 to 45 days and the optimal temperature for germination is 60 to 65 degrees F.
The University of Maryland Medical Center reports that yarrow has historically had three primary medical uses: as a topical application for wounds and to stop minor bleeding; to alleviate digestive inflammation; as an aid for insomnia and anxiety. The center also states that modern herbalists use yarrow for a wide range of medical problems such as heartburn, loss of appetite, muscle spasms and fever. Yarrow contains chemicals called flavinoids that might explain its medicinal efficacy. However, the scientific studies done on the plant as of March 2011 have not proved conclusive.
Though the use of herbs for medicinal purposes has a long history, herbs -- like conventional medications -- can have side effects or interact with other drugs. A sensitivity to other aster family plants such as daisies or ragweed might indicate a sensitivity to yarrow. Pregnant women in particular should avoid yarrow as it might lead to miscarriage. The herb might also make your skin more sensitive to sunlight and interfere with drugs that reduce stomach acid. Consider taking yarrow only after consulting a health care professional.
Yarrow makes a good companion plant for a vegetable garden, according to master gardener Lesa Shields of the University of Idaho Extension. Secretions from its roots might help other plants resist insects and disease. Yarrow grows well on most soil types and is drought tolerant. Deadheading blooms when they start to fade promotes the growth of more blossoms. Yarrow spreads quickly and becomes invasive if not controlled.