Carpetweed

About

Carpetweed is a flat, mat-forming summer annual that shows up in warm, bare soil later than most weeds. It is shallow-rooted and easy to pull, but it spreads into circles up to 2 feet across and reseeds freely.

Also called green carpetweed

How to identify it

Look for

Smooth, green stems radiate flat from the center, rarely more than 5 inches high. Narrow, smooth leaves grow in whorls of 3 to 8 at each joint, and tiny white five-parted flowers sit at the joints from midsummer to early fall.

Look-alikes

Catchweed bedstraw has a similar whorled look, but its square stems and leaves are bristly, it grows more upright, and its flowers have four parts instead of five.

Where it grows

Tilled vegetable gardens, new lawns, flower beds, roadsides and dry, sandy, disturbed ground.

When

Sprouts late in spring or early summer once the soil is warm, then flowers and seeds from midsummer into early fall.

How it spreads

Seed only; each small capsule holds up to 35 seeds and plants reseed readily into colonies.

Most common in

What to do, gentlest first

Start at the top. Weed killers are a last step; always read and follow the label.

1. Keep turf and beds full Prevent

   It can't handle shade, so a thick, well-kept lawn and full plantings crowd it out. Pull it before it flowers to stop seed.

2. Pull or hoe By hand

   The roots are shallow, so plants pull or hoe out easily; do it before midsummer flowering.

3. Mulch Barrier

   Mulch greatly reduces or prevents it in gardens.

4. Burn down seedlings with a contact spray Organic spray

   Horticultural vinegar (acetic acid), fatty-acid soap, pelargonic acid or clove-oil sprays burn what they touch within hours. They work best on young mats in warm, sunny weather, and you will need to repeat, because they don't move into roots and bigger plants regrow.

   They kill any plant they touch, so shield crops. Strong vinegar can burn skin and eyes; wear goggles and gloves and follow the label.

5. Pre- or post-emergent herbicide Conventional spray

   Purdue lists S-metolachlor, flumioxazin and DCPA as pre-emergents and flumioxazin, glyphosate or 2,4-D after it's up, for crops they are labeled for. Carpetweed can also host root-knot nematodes.

   Read and follow the label. Many lawn weed killers also kill or damage vegetables and flowers, so keep spray and drift off garden plants.

Uses, wildlife and pets

Edible?

Wisconsin Extension notes the leaves are edible when cooked. Only eat plants you are sure of, from soil that hasn't been sprayed.

Not 100% sure? Don't eat it. Never pick from ground that may have been sprayed, or along roads and railways.

For wildlife

Birds and small mammals eat the seeds, and small flies and bees visit the flowers (Wisconsin Extension).

Pets

Not listed by the ASPCA.