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 Achillea is derived from mythical Greek character Achilles, who reportedly carried it with his army to treat battle wounds. The specific epithet millefolium as well as the common names milfoil and thousand leaf come from the featherlike leaves which are minutely divided. The English name yarrow comes from its Saxon (Old English) name gearwe, which is related to both the Dutch word gerw (alternately yerw) and the Old High German word garawa. In the eastern counties it may be called yarroway. In France, it was called 'herbe de St. Joseph' after a Christian revision of the Achilles story, in which Jesus uses the plant to heal his adoptive father. It has also been called 'carpenter's weed' in this regard. Other names include arrowroot, nose bleed, death flower, eerie, hundred leaved grass, knyghten, old man's mustard, sanguinary, seven-year's love, snake's grass, soldier, and gordaldo. In New Mexico and southern Colorado, it is called plumajillo (Spanish for 'little feather') from its leaf shape and texture. Distribution and habitat Yarrow grows from sea level to in elevation. Common yarrow is frequently found in the mildly disturbed soil of grasslands and open forests. Active growth occurs in the spring. The plant is native to Eurasia and is found widely from the UK to China. 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. 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. Ecology Birds 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 that adding yarrow to nests inhibits the growth of parasites. Insects Achillea millefolium is a food source for many species of insects. Moths The larvae of the moths Bucculatrix clavenae, B. cristatella, B. fatigatella, B. humiliella, B. latviaella, Cnephasia abrasana, Cochylimorpha elongana, Coleophora argentula, C. carelica, C. ditella, C.