Carpetweed

Carpetweed is a low, prostrate summer annual broadleaf weed that spreads its smooth, slender, much-branched stems flat across the ground to form distinctive circular mats. Its small, light-green, lance-shaped to spoon-shaped leaves are arranged in whorls of three to eight at each node, a key identifying trait. Tiny white five-petaled flowers appear in small clusters of two to five at the leaf nodes through the summer. The plant has a relatively shallow root system. The whorled leaf arrangement and flat, radiating mat habit distinguish it from other prostrate summer weeds such as spurge and knotweed.

Carpetweed forms flat, spreading mats that cover bare and thin areas of turf, creating light-green patches of contrasting texture that interrupt a uniform lawn and press over the soil surface. Because it grows quickly and spreads outward, it occupies and competes for space in newly seeded or weak turf, slowing grass establishment and leaving open, mat-covered voids that detract from the density and appearance of the stand until the plant dies back at frost.

Carpetweed is a summer annual that reproduces entirely by seed and completes its life cycle within a single growing season. It germinates relatively late, in late spring once the soil is warm, then grows and spreads rapidly across open ground, flowering and setting seed through summer before dying at frost. Its quick development and prolific seed production let it colonize bare soil swiftly and build a seed bank that drives reinfestation the following year.

Carpetweed favors sunny, disturbed, open sites and is most common on dry, sandy soils, though it also tolerates moist ground. It readily invades newly seeded or thin lawns, tilled gardens, and bare areas along edges and roadsides where open soil and full sun let its late-spring seedlings establish without competition. Thin, young, or recently disturbed turf with exposed soil in summer is the prime situation for infestation.