Smooth Crabgrass

Digitaria ischaemum

Weed Description
Summer annual, having a prostrate or ascending growth habit, with leaves and sheaths that do not have hairs and stems that do not root at the nodes. Found throughout the United States.

Seedlings
Sheaths and blades not hairy, few hairs at mouth only, with a jagged membranous ligule. Seedlings are upright, leaves are rolled in the bud, and the first leaf blade is lanceolate to linear.

Leaves
Blades 5-14 cm long, 2-7 mm wide, without hairs. Sheaths are without hairs and closed, with hairs in the collar region only. Ligules are 1-2 mm long, membranous with even margins. Leaves and sheaths may turn dark red or maroon with age.

Stems
Prostrate or lying on the ground with tips ascending (decumbent) up to 60 cm long, branching at lower nodes but not rooting.

Flowers
Seedhead composed of 2-6 branches (spikes) at the top of stems, each 10 cm long. Spikelets 1.8-2.1 mm long, 0.8-0.9 mm wide, in two rows along the spike, with short mushroom-like hairs.

Roots
Fibrous root system.

Identifying Characteristics
Sheath and leaves without hairs, mushroom-like hairs on spikelet. May be distinguished from Large Crabgrass (Digitaria sanguinalis) by the absence of hairs on the leaves and sheath, and only a few hairs found in the collar region. Additionally, smooth crabgrass does not root at the nodes like large crabgrass.

Office of Programs

University of Missouri

Smooth Crabgrass

Digitaria ischaemum