Yarrow: Weed or First Aid Kit?

Yarow in the Apple Guild.

       Yarrow is an invasive weed. I wasn't aware of this years ago when I discovered the flowering plant in a flower shop. I liked both the white and pink blooms and the feathery leaves and, in my ignorance, purchased a few plants and added them to my landscaping. They made themselves at home and spread before I learned their true nature and started deadheading and digging them out. "Digging" is the operative word, because it spreads through roots as well as the 1600 seeds a single plant can produce in a year.  I was, of course, unsuccessful in eliminating what I believed to be a nuisance plant.        Fast forward a few years and copious reading about herbs. Yarrow's nature hasn't changed; it's as invasive as ever. I've learned to recognize the plant growing wild in the fields around our farm, and I marvel that I actually paid money for what nature provides so abundantly. What we know as common yarrow is not native to the U.S. Apparently, its ancestors immigrated and inter-bred with a related native species and ones imported from Asia. What I purchased is something different, as common yarrow, I read, doesn't survive cultivation. I'm relieved now that my earlier efforts to eradicate it failed. I moved some of the survivors to the apple guild, where they can thrive and spread with my blessing. As plants in a guild should, yarrow provides more than one function. It's a ground cover. It repels Japanese beetles, ants and flies; its root secretions help the disease resistance of nearby plants; and its presence increases the essential oils in nearby herbs.
       On top of all this, a single fresh, finely chopped yarrow leaf  added to a wheel barrel of raw compost will speed composition.
       The plant has a history of conjuring powers. Want to identify your future true love? Sew an ounce of yarrow into a small flannel square and place it under your pillow, recite the requisite poem, and see him/her in your dreams. Druids used yarrow stems to predict weather and Chinese I Ching masters foretold the future by reading fifty thrown yarrow stems.   
      With all these uses, how can we possibly classify yarrow as a weed? And there's more! Finely chop young leaves and add to salads and soft cheese dips for a peppery, slightly bitter taste. Use leaves as a garnish. In a pinch, substitute yarrow for cinnamon or nutmeg. Chewing fresh leaves helps to relieve toothache. A leaf infusion can prevent baldness; so one source claims, anyway. Sources agree that an infusion flavored with honey and Tabasco sauce will cause profuse sweating to help break a cold-related fever. Yarrow has been used as a hops substitute in making beer. A flower infusion serves as a facial steam and tonic lotion to treat greasy skin.
       Last year my husband and I were checking on some seedling trees we had planted in one of our overgrown fields. I scratched my hand on the wire cage protecting one tree from deer an rabbits. Since I didn't have anything to treat the wound, I ignored the bleeding. Later the same day, I learned that yarrow is used to staunch blood flow. Legend has it that yarrow was used during the Trojan Wars to treat Achilles's warriors' wounds, thus the name Achillea millefolium. My seedling trees nested among yarrow plants. A decoction made from leaves treats wounds, chapped skin and rashes.
       Don't forget that the flowers are attractive, suitable for cutting and drying, and the plant makes a terrific border--if you don't mind that it spreads. Flowers appear from June to October, and even into November when the photo above was taken. Unlike many weeds, frequent mowing doesn't kill yarrow. Instead it adapts, and becomes a ground hugger. One source suggested using sheep as a control. Or let deer browse on it.
       For the uninitiated (I had to look this up) an infusion is boiled water poured over herbs and left to steep, covered, strained and used or refrigerated (up to three days). In a decoction water is added to the herb and brought to a boil, simmered until the liquid is reduced to half, then cooled, strained, and used or bottled and refrigerated. I recommend more research before you try this. Keep in mind that too much yarrow use can make your skin sensitive to light, and beware of possible allergic reactions like rashes, dermatitis and eczema.
       I  consulted more than one source for this post, but mainly used The Complete Book of Herbs, a practical guide to growing and using herbs, by Lesley Bremness.