Scientific Name: Digitaria sanguinalis

Common Name: hairy crabgrass

Other Common Names: large crabgrass, purple crabgrass

Synonyms: Panicum sanguinale, Syntherisma sanguinalis

Habit: Large crabgrass germinates in the spring and competes with turf during the summer months. Crabgrass begins germinating when sustained soil temperatures are 55 degrees F and moisture is available. In Virginia (USA) plants usually begin germinating mid April to early May in the mountains, late March to late April in the piedmont, and early March to mid April on the coastal plain. Plants compete with turfgrass during the summer, set seed in the fall, and die with first frost.

Leaves: Large crabgrass leaves are densely hairy on both surfaces. Hairs are long but stiff and erect. The collar area and stems are hairy and the ligule is a large membrane. Stems tend to trail along the ground and root at nodes.

Identifying Characteristics: Fat cotyledon (seed leaf), hairy on all leaves and stems, large membraneous ligule and three to five-branched seedhead on slender stalk.

Flower Seed Head: Seedheads are borne on slender stalks and consists of three to five spikelets in an open arrangement.

Seed Fruit: Seeds are flat and narrow; about 1.5 mm wide and 5 mm long.

Where Found: Large crabgrass is widely distributed and one of the most economically important weeds of turfgrass. Plants can be found in the lawn, under close cut such as a putting green, and in tilled areas such as a home garden.

  • Life cycle: summer annual

  • Plant type: Grass

  • Auricle: not present

  • Plant family: Poaceae

  • Leaf arrangement: rolled in bud

  • Hair surface: hairs from base to tip

  • Ligule: membrane

  • Length: 1-2 mm; 2-3 mm; less than 1 mm

  • Root structure: fibrous

  • Seed head: multiple spikes

  • Width: less than 5 mm; 6 to 15 mm

  • Grass stem: flat or oval