Yarrow is a member of the Asteraceae family, along with sunflowers, daisies, and many others. It grows up to three feet tall with flat composite flower heads.
Insects love this plant! Of interest to gardeners is Yarrow’s attraction for ladybug larvae and parasitic wasps. Bees, butterflies, and other pollinators are also drawn to this bright and happy flower.
Ladybug larvae are aphid-eating machines. Use Yarrow as a companion plant next to tomatoes or other vegetables to greatly reduce the aphids in your garden. Parasitic wasps lay eggs in the larval form (caterpillars) of several garden pests, eventually killing them. Perhaps the most important of these for a gardener is the tomato-destroying Hornworm.
Folkore tells us that herbs also love growing nearby. Planted next oregano, basil, thyme, dill, or lavender, it will intensify their flavor and essential oils.
Yarrow for Mulch & Compost
Yarrow is thought to be a “dynamic accumulator” by Permaculture practioners, with it’s deep roots mining nutrients, which are stored in the leaves. Thus it makes an excellent compost, or a “chop and drop” mulch. Don’t worry about cutting down too much of the plant. It will surely come back up from the deep roots and rhizomes.
Thanks to hybridization, Yarrow comes in many colors. Herbalists will tell you that when you hybridize for color, you may lose some beneficial properties. So if your intent is to use it medicinally, look for native-grown plants. Native plants will usually display yellow or white flowers. Use with caution if you are allergic to asteraceae plants, such as dandelions or ragweed.
Yarrow as an ornamental
Although Yarrow makes a great companion to larger plants like tomatoes, it may crowd out less vigorous growers. Fortunately, gardens can reap the benefits of yarrow planted nearby, such as in a border. This plant looks fantastic combined with coneflower, zinnias, black-eyed Susans, sunflowers, and ornamental or native grasses.