Digitaria ischaemum aka Crab Grass

Digitaria ischaemum is an annual grass in the Poaceae family. Its common names include smooth crabgrass and small crabgrass. Its native range spans east-central and southern Europe to northern and central Japan. It is not native to Britain or Ireland. It grows in temperate regions and thrives during warm weather. In the United States, it occurs across most states. It grows in lawns, meadows, road verges, and disturbed ground. It also takes hold in cracks in sidewalks.

This grass forms low clumps that spread along the ground. Some stems rise above the spreading growth. It grows fast and can root where leaf nodes touch soil. These extra roots make older plants hard to pull out. The stems are round and smooth, with no scent. They range from pale green to purple near the base. Leaf sheaths cover much of each lower stem. The flat, narrow leaves have smooth edges and green blades. Blades reach about 0.33 feet [0.10 metres] long. Their width reaches about 0.02 feet [0.006 metres]. The ridged sheaths open along the front. A few long hairs grow on them and near their bases.

Flowers appear in summer and fall. The small blooms lack a showy display. Flowering stems end in racemes with small, egg-shaped spikelets. These spikelets tend to grow in pairs along the stalk. As they mature, they turn brown or take on purple tones. They form oval seeds that become dark brown to black. The source describes the fruit as an achene. Fruit develops during summer and fall, completing the annual seed cycle.

Smooth crabgrass grows in full sun and tolerates partial shade. It favors heavier soils, but also grows in loam and shallow, rocky soil. It suits well-drained ground that stays moist or sometimes dries out. It tolerates both heat and drought. Seeds sprout from late winter into early spring. Plants grow through summer and produce more seed. Frost kills the plants rather than leaving a lasting clump.

Its main garden role is as a weed. Rooting stems make control harder as the season goes on. Pull young plants before they form extra roots. Mulch on garden beds can reduce seed germination. The supplied evidence gives no food uses or toxicity assessment.