PROSTRATE KNOTWEED, Polygonum aviculare L. 1, entire plant; 2, seeds; 3, portion of stem and leaves; 4, single leaf; 5, distribution. Annual, reproducing by seed. Stems bluish-green, leafy, wiry, extending 4 to 24 inches (10 to 60 cm) in all directions from the small taproot and forming a dense mat. Each joint or node covered with a thin papery sheath. Leaves bluish-green, alternate, oblong, narrowed at base, pointed at tip. Flowers very small, yellow or white, borne in clusters in the leaf axils. Seeds small, slender, reddish-brown, triangular. Found in hard trampled areas in yards, lawns, waste places, and along roadways or paths.

 ERECT KNOTWEED, Polygonum erectum L. 6, branch of plant; 7, portion of stem and leaf; 8, leaf; 9, distribution. Annual, reproducing by seed. Stem erect, 8 to 24 inches (20 to 60 cm) high, branched near top, smooth, yellowish-green, slightly rigid. Leaves light green, oval, alternate, 1/4 to 1 inch (0.6 to 2.5 cm) long, sometimes covered with mildew. Flowers and seed similar to those above. Found in same areas as prostrate knotweed.