What is carpetweed?

Carpetweed identification is simple once you know the trick: look for narrow leaves arranged in whorls, like the spokes of a wheel, on stems that lie flat against the ground. It’s a summer annual that sprouts once the soil warms up and dies with the first hard frost.

Carpetweed shows up wherever there’s bare, warm soil: freshly turned garden beds, thin spots in a new lawn, the gap between pavers and mulch, and sunny gravel edges. It doesn’t compete well with thick grass or deep mulch, so it’s mostly a sign that the soil is exposed.

Unlike a lot of weeds on this list, it’s generally considered native to the Americas. That doesn’t make it welcome in your vegetable garden, but it’s not an invasive threat to the woods.

Carpetweed identification: what to look for

A single plant can spread into a circular mat over a foot across, rooted at one central point.

• Leaves: narrow and spoon-shaped, wider near the tip, up to about 1.5 inches long. They grow in whorls of three to eight at each joint.
• Stems: smooth, hairless and branching outward from the center in a flat star or circle.
• Flowers: tiny, white and five-parted, sitting on short stalks at the leaf joints, mostly from July into September.
• Seeds: each flower makes a small capsule packed with tiny orange-brown seeds.
• Roots: one shallow taproot. Grab the center and the whole mat comes up.

Run your fingers over it. Carpetweed feels smooth, which separates it right away from bedstraw and other sticky or hairy look-alikes.

Where it grows in Pennsylvania

You’ll find carpetweed across the state in vegetable gardens, annual flower beds, nursery and field edges, and anywhere soil has been disturbed and left open in summer. It likes hot, sunny spots and does fine in sandy or compacted ground.

Around homes, the usual hot spots are newly seeded lawns, the soil strip along a driveway or walk, the edge of a paver patio, and garden beds where the mulch has thinned out. It also loves the bare soil left after a construction or grading project.

Because it waits for warm soil, carpetweed usually shows up later than spring weeds like chickweed and henbit. In central PA that typically means late May or June, and it keeps sprouting through summer whenever you leave soil open after pulling other weeds.

Carpetweed look-alikes

Several low summer weeds form mats, so check the leaf arrangement first.

Spotted spurge grows in the same hot, bare spots, but its leaves are in opposite pairs, often with a reddish blotch, and broken stems ooze milky sap. Purslane has thick, juicy leaves and yellow flowers. Chickweed has paired leaves and prefers cool weather. Catchweed bedstraw does have whorled leaves, but its square stems cling to your clothes with tiny hooks.

How to get rid of carpetweed

For most homeowners, hand pulling is the right answer. The shallow taproot comes out easily, especially when the soil is damp.

• Pull or hoe early: get plants in June and July, before the white flowers turn into seed capsules. A sharp stirrup hoe slices young mats off just below the surface.
• Mulch beds: a 2 to 3 inch layer of shredded bark or wood chips blocks the light carpetweed seeds need to sprout. Keep the layer topped up where it’s worn thin.
• Thicken the lawn: seed or sod bare spots, mow at about 3 inches, and fertilize on schedule so grass fills in and shades the soil.
• Chemical options: Penn State lists preemergence herbicides such as dithiopyr for turf and several bed products for ornamentals, applied before the soil warms in late spring. Glyphosate or a three-way lawn broadleaf product containing 2,4-D, dicamba and MCPP will knock out existing plants, but they’re rarely needed for a weed this easy to pull.

If you do use an herbicide, read and follow the label (the label is the law) and make sure it’s labeled for your site, whether that’s lawn, flower beds or a vegetable garden. Applying herbicides for hire in Pennsylvania requires a PA Department of Agriculture pesticide applicator certification, so larger jobs belong with a licensed lawn-care company.

Keeping it from coming back

Carpetweed only spreads by seed, so the best long-term move is never letting it flower. A few minutes of pulling each week in midsummer drains the seed supply in the soil over a couple of seasons.

Cover the ground. Keep beds mulched, plant groundcovers or tighter spacing so plants shade the soil, and get bare lawn spots seeded in late summer or early fall when grass establishes best. In paver joints, swept-in polymeric sand leaves far less room for seeds to sprout than plain sand. See our polymeric sand vs. regular sand guide for details.

Questions we get about carpetweed

Similar weeds

Spotted SpurgeEuphorbia maculataCommon PurslanePortulaca oleraceaProstrate KnotweedPolygonum aviculare