Achillea has a dozen nicknames including yarrow, old man’s pepper, milfoil, thousand-leaf, wound-wort, devil's nettle and others. The species name, millefolium means thousand-leaf. That name comes from yarrow's many toothed leaves.
Yarrow is the most commonly used name for all the varieties that are available. It is an easy to grow herbaceous (dies to the ground in the winter) perennial that will come back year after year. The wild, white flowering, variety that grows in fields has been tamed over and over again, making garden yarrow into a reliable and beautiful perennial. All yarrows have flat flower-heads containing dozens of small, flowers that are ignored by deer. The green or grey-green leaves are feathery and scented or aromatic.
Gardeners who want cut flowers for the house cannot resist long-lasting yarrow blooms. The flower heads are 2 to 6-inches across on 18- to 24-inch stems that will fill several vases. After cutting or deadheading, the plants will re-bloom. Flower colors include white, ivory, yellow, gold, coral, pink, red, lilac, purple, etc. The newest varieties have stronger stems and larger flower heads than the heirlooms.
Yarrow prefers 8 hours of sun a day and lean, unfertilized soil that stays on the dry side. Shady locations can cause lanky stems that fall over. Humidity and heat are no problem for any yarrow but it will tend to sprawl. The common variety, Achillea millefolium, spreads vigorously.
Yarrow blooms for a month or two, attracting ladybugs, butterflies and syrphid flies. Syrphid flies, also called hover flies, are harmless to us but their caterpillars eat dozens of harmful insects such as aphids. After the summer flowers fade, cut back the plant stems to keep them compact as well as encourage new growth and re-blooming in the fall.
During the growing season, the plant's roots can be divided into several pieces and replanted. Just snip off the faded flowers first. Or, if you prefer, take soft (not woody), tip cuttings and grow them in pots to make a supply of identical plants. Crafters often use the flower heads for dried arrangements. To dry them, cut before they fully mature and hang them head down, in a breezy place, away from sunlight. Yarrows can be started from a packet of seed but most gardeners purchase plants to get the varieties that are propagated from cuttings.
Achillea was named after Achilles. You may recall from high school that Achilles was the Greek hero of the Trojan War in Homer's Iliad. The plant's names of soldier's staunch weed and woundwort come from its early medicinal use of blood clotting. Achilles was said to carry a supply of the plant into battles. One name, old man's pepper, came from the days men used the dried leaves as snuff.
Yarrow also has somewhat spiritual properties. It was believed that if a single man or woman put an ounce of yarrow under their pillow at night they would have a vision of their spouse to be while sleeping. Today, yarrow tea is used to treat colds and flu and is a component of herbal cosmetics. Yarrow is a member of the Asteracaea plant family which includes aster, daisy, mums and sunflower.