Prostrate pigweed

Amaranthus blitoides

Prostrate pigweed is a native mat-forming summer annual weed that invades thin, damaged or under-fertilized lawns. It is common in areas with disturbed soils or neglected areas. Prostrate pigweed lacks the hairs common to redroot pigweed and has smooth leaves.
Leaves small (blade about 1 in) with distinct notch at tip; seeds dull black, larger than in other pigweeds (0.06 in).