Virginia Tech Weed Identification Guide

Large Crabgrass: Digitaria sanguinalis

Weed Description:   Summer annual, having a prostrate or ascending growth habit with stems that root at the nodes. Major distribution in North America from Canada south to Virginia, Kentucky, and Texas, west to California. Usually not found in the lower south.

Stems:  Prostrate, spreading, branched, and rooting at the nodes.

Seedling:  Sheaths and blades usually densely hairy, with a jagged membranous ligule. Hairs on the blade and sheath are at a 90 angle to the plant surface. Seedlings are upright, leaves are rolled in the bud, and the first leaf blade is lanceolate to linear.

Roots: Fibrous root system.

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Leaves:  Blades 1 1/4 to 8 inches long, 3-10 mm wide, with hairs on both surfaces. Sheaths hairy and closed. Ligules are 1-2 mm long, membranous and appearing as if cut off straight across the end, with uneven teeth or margin. Leaves and sheaths may turn dark red or maroon with age.

Flowers: Seed head composed of 4-6 branches (spikes) at the top of stems, each approximately 1 1/2 to 7 inches long. Spikelets are elliptic and in two rows along the spike.

Seed:  Shiny, yellowish-brown, 2-3 mm long.

Identifying Characteristics:   Densely hairy leaf and sheath and relatively large membranous ligule. Similar in appearance to Smooth Crabgrass (Digitaria ishaemum), but smooth crabgrass does not have hairs on leaves and sheaths, only a few hairs may be found in the collar region. Additionally, large crabgrass roots at the stem nodes while smooth crabgrass does not.