Large Crabgrass

Large Crabgrass, Digitaria sanguinalis 

Other names: Finger grass, hairy crabgrass, hairy fingergrass, digitaire sanguine

 


Crab Grass Blade

Origin and distribution
According to many sources, large crabgrass is native to Europe; however, USDA-PLANTS (plants.usda.gov) indicates that it is native to the continental United States. Regardless, large crabgrass is widespread in the United States and also occurs elsewhere in temperate (including Canada) and tropical regions of the World. Large crabgrass is a widely distributed summer annual grass that germinates throughout the summer. It inhabits crop fields, orchards, vineyards, gardens, landscaped areas, turf, nurseries, pastures, roadsides, ditches, and other disturbed places. Once established, it is difficult to remove because it roots from portions of lower stems. It can provide good forage for livestock.

Plant description

It is a summer annual with a prostrate or ascending growth habit with stems that root at the nodes. It has dense 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.

Root system
Large crabgrass has a fibrous root system.


Crab Grass Shoots

Seedlings and Shoots
Seedlings sprout quickly. They are pale green and covered with coarse hairs, 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.

Stems
Stems are prostrate, spreading, and branched, and roots at the nodes.

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


Crab Grass Seeds

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

Fruits and Seeds
Seeds are shiny, yellowish-brown and are 2-3 mm long.

Management

Cultural Practices
Elevated mowing heights and judicious nitrogen fertilization can be extremely effective at reducing competition from crabgrass. Research studies have shown up to 95% reduction in crabgrass when mowing height is increased from 1.5 to 3.0 inches. Thin turf in the spring or drought conditions often leads to major infestations of crabgrass.

References:

California Statewide Integrated Pest Management Program

Virginia Tech Weed Identification Guide

Invasive Plant Atlas of the Midsouth

Department of Crop and Soil Sciences, Michigan State University