Several stems branch from the yarrow’s rootstalk to support its foliage. The six-inch, feathery leaves grow from stems that branch from the rootstalk. They have a fern-like texture, making yarrow an attractive plant even when it’s not in bloom. Plant your yarrow in spring or early summer. They don't need a rigorous watering schedule but require at least an inch of water each week. Humidity isn’t a problem. Well-drained sandy loam or sandy clay soil that isn’t too rich or fertile works best. Yarrow prefers full sunlight, but it doesn’t mind a bit of shade, either.

Because it is such a prolific grower and can become invasive, some people consider wild-growing yarrow to be a weed. The self-sower spreads by rhizomes to a width of two feet, so allow for about 24 inches between each plant when setting. If you have a difficult patch in your yard where nothing seems to grow, try planting yarrow there. Keep it happy, and your yarrow will return year after year for a decade or more.

Most yarrow varieties grow to four feet in height, although some only reach about 18 inches. Yarrow grows clusters of umbrella-shaped flowers that bloom in golden yellows, deep pinks, vivid reds, rich purples, and assorted pastels.

Yarrow is low-maintenance, but still requires a bit of attention. In most locales, the early summer blossoms start to fade and die in mid-summer. If you allow the flowers to dry out on the plant, they’ll go to seed and spread around the garden. Once they fade, cut off or deadhead the yarrow’s blooms to encourage more flowering. Every three to five years, in the early spring or fall, divide the yarrow clumps into separate plants and replant, or gift them to fellow gardeners.

For some people, yarrow causes an allergic skin reaction, so wear gloves when doing any clean-up or pruning of the plant. Pruning prevents the yarrow from getting out of control and encourages blooming. If you see the stems flopping over, reduce the plant's height. Once the blooming season ends, cut the entire stem down to the lowest foliage near the ground, but don’t remove these leaves. They’ll protect the plant through the winter months.

A white powder on the leaves of your yarrow plants is likely botrytis mold or powdery mildew. You can treat this with a fungicide. A common pest drawn to yarrow is the spittlebug, which produces a protective foam that looks like saliva. A strong spray of water will wash away the foam, leaving the insects unprotected. Exposure to UV light will, in most cases, kill them. Use an insecticide if you continue to see evidence of the pest.

Yarrow may have medicinal possibilities for humans, but avoid planting it where your pets have access to it. Although it has a bitter taste that dogs and cats don’t like, it’s best to use precaution. Yarrow contains achilleine, which is toxic for dogs and cats and causes photosensitivity in horses. Increased urination, vomiting, diarrhea, and dermatitis are symptoms of consumption in animals. If you suspect your pet has eaten yarrow, contact your veterinarian.

Numerous studies show that yarrow soothes irritable bowel syndrome symptoms. Herbalists say it stimulates blood circulation, lowers blood pressure, and normalizes other bodily functions. The plant contains antimicrobial properties that prevent infection and it helps stop bleeding when applied to a cut or wound. Some people use yarrow in poultices, soaks, and salves to relieve pain. Others say it is an excellent treatment for stress and anxiety.

The Latin name for yarrow, Achillea, has ties to the Greek hero, Achilles, a skilled warrior famous for his part in the Trojan War. Greek stories say he was also famous for his medical knowledge, a skill he learned frp, the centaur physician, Chiron. Achilles used a "miracle" plant, identified by historians as yarrow. It clotted the soldiers’ wounds and stopped the bleeding. Yarrow also has a long history in the magical world as a plant of protection and a symbol of everlasting love.