General Description: A summer annual with erect,
Seedling: The first leaf blade is linear and opens parallel to the ground. Leaves are rolled in the bud, lack auricles, and have no ligule. Blades are 2.8 to 5.5 in (7 to 14 cm) long and 0.1 to 0.2 in (3 to 5 mm) Mature Plant: Leaves are similar to those of seedling, and ligules are absent. Blades are about 4 to 8 in (10 to 20 cm) by 0.2 to 0.8 in (5 to 20 mm), lack hairs, and are smooth to somewhat rough on both surfaces. The midvein is distinct and keeled in the basal portions of the leaf. The collar is whitish, broad, and smooth. Sheaths are open, compressed, and smooth, but sometimes have a tuft of short hair at the base. Culm is stout, tufted arising from a jointed base which trails along the ground. Flowers and Fruit: Flowering occurs from July to September. The panicle is a coarsely branched green to purplish. Spikelets contain one perfect floret, round, slightly flattened, somewhat rigid, covered with stiff hairs on glandular bumps, membraneceous tip set off from from the body by a line of minute hairs. Glumes may be awned with the length of the awns varying among biotypes. The seed is shiny, oval, and brownish with longitudinal ridges. Distribution: Found throughout the United States. Crops Affected: Corn, Soybean Animal Poisoning: None Similar Species: Large crabgrass is similar to broadleaf signalgrass when they are a small seedling. However, crabgrass is hairy on the sheaths.