What is yarrow?

Yarrow is a tough perennial in the aster family that’s equally at home in a wildflower meadow and a thin lawn. Accurate yarrow identification is easy once you’ve seen its feathery leaves, and it helps you decide whether it’s a weed or a welcome plant where it’s growing.

Yarrow spreads by creeping underground stems and by seed. In a lawn that gets mowed regularly, it hugs the ground and forms a dense, soft mat. Left alone, it sends up flower stalks 1 to 3 feet tall with flat clusters of tiny white flowers.

Some yarrow is native to North America, and European forms were also brought over and have mixed in. Many gardeners grow yarrow on purpose, and pollinators love it. It isn’t on Pennsylvania’s noxious weed list.

Yarrow identification: what to look for

The leaves are the giveaway, even in a mowed lawn where the plant never flowers.

• Leaves: soft, gray-green and finely divided, like little feathers or fern fronds.
• Smell: crush a leaf and you’ll get a strong, spicy, herbal scent.
• Flowers: flat-topped clusters of many tiny white flower heads, sometimes tinged pink, in summer.
• Stems: upright, slightly hairy flower stalks where it isn’t mowed.
• Spread: underground runners connect plants into patches.

Where it grows in Pennsylvania

Yarrow does best where lawn grasses struggle: dry, sunny, low-fertility soil. Around central PA, look on south-facing banks, sandy or gravelly spots, the strip along a hot driveway, roadsides, old farm fields and lawns that haven’t been fed in years.

It handles drought far better than most turf, so it often spreads during a dry summer while the grass goes dormant. On thin, rocky soils that dry out fast, yarrow can end up being a large part of what stays green in August.

You’ll rarely see it in shady, moist lawns or in turf that’s fed and watered regularly. If it’s showing up in one part of the yard and not another, compare the two spots. The yarrow side is almost always the sunnier, drier or poorer-soil side.

Yarrow look-alikes

Several plants in the carrot family have similar lacy white flowers, and one of them is dangerous, so it’s worth a careful look. Queen Anne’s lace has bigger, lacy flower umbrellas and a hairy stem. Poison hemlock grows much taller, with smooth, purple-spotted stems, and it’s highly poisonous, so don’t handle any tall, white-flowered plant bare-handed until you know what it is.

Wild chervil blooms in spring with broader, parsley-like leaves. Pineappleweed has feathery leaves too, but its small, cone-shaped yellow-green flowers have no white petals.

How to get rid of yarrow

Mowing alone won’t get rid of yarrow; it just makes it grow flatter and denser. Real control means removing the runners or making the lawn strong enough to crowd it out.

• Dig small patches: use a garden fork or hand weeder in moist soil and lift out as much of the underground runners as you can. Pieces left behind can resprout, so check back a few weeks later.
• Pull from beds: in planting beds, pull plants and runners, then cover the soil with mulch.
• Stop seeding: cut flower stalks before seed ripens in fall.

Cultural control. Yarrow is a sign of thin, hungry turf. A soil test through Penn State Extension tells you what your lawn actually needs, and fertilizing to match is the single biggest step. Overseed thin areas in early fall, mow at a taller height, and water deeply during long dry stretches. Core aeration helps on compacted soil. As the grass thickens, yarrow loses ground.

Chemical control. In lawns, selective broadleaf herbicides containing 2,4-D, MCPP (mecoprop), dicamba or triclopyr are the ingredients extension services commonly list. Yarrow is fairly tough, so combination products and more than one application are often needed. Apply while it’s actively growing, ideally in early fall, with a follow-up in spring. Don’t spray dicamba over the root zones of trees and shrubs. Read and follow the label, which is the law, and confirm the product is labeled for your lawn or beds. Applying herbicides for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so a full lawn program belongs with a licensed lawn-care company.

Keeping it from coming back

Keep the turf fed and thick, and yarrow has a hard time getting started again. Test your soil every few years, overseed in early fall, and keep your mower set high.

On steep, dry banks where grass will always struggle, it may make more sense to let yarrow and other tough plants have the slope, or to convert it to a mulched planting. Plenty of homeowners in central PA keep yarrow in a sunny bed on purpose as a drought-tough pollinator plant.

Questions we get about yarrow

Similar weeds

Queen Anne's Lace (Wild Carrot)Daucus carotaOxeye DaisyLeucanthemum vulgareWhite CloverTrifolium repens