Scientific Name: Digitaria ischaemum

Common Name: smooth crabgrass

Other Common Names: small crabgrass

Synonyms: Digitaria ischaemum var. mississippiensis, Panicum ischaemum, Syntherisma ischaemum

Habit: Although smooth crabgrass typically acts as an annual, it may persist as a perennial. Typically, smooth crabgrass germinates in spring, grows during the summer, sets seed in the fall, and dies in the winter. Smooth crabgrass can withstand close mowing heights and is highly competitive with desirable turfgrass

Leaves: Leaves have smooth edges and typically lack hairs. Veins are inconspicuous and the leaf surface is smooth and light green.

Identifying Characteristics: Smooth crabgrass usually lacks hairs unlike large crabgrass or southern crabgrass which are completely hairy and marginally hairy, respectively. Smooth crabgrass has a large membranous ligule like other crabgrass plants. Older smooth crabgrass plants are red at the base of the plant. The collar area is usually smooth but may have a few short hairs.

Flower Seed Head: Seedheads have three to five spikelets with multiple seeds in an open arrangement. Spikelets are borne on a slender smooth stalk and are usually about 8 inches tall but may be much shorter if the area is mowed regularly.

Seed Fruit: Seed are light brown and about 1/16 to 1/8 inch long and about 1/16 inch wide. Seed are pointed at both ends and flat to oval in thickness. Seed may have short hairs.

Where Found: Most types of turfgrass. May tolerate close mowing typical of putting greens or close-cut fairways. Smooth crabgrass and large crabgrass make up most of the crabgrass populations in Virginia lawns and turfgrass areas.

  • Life cycle: summer annual

  • Plant type: Grass

  • Auricle: not present

  • Plant family: Poaceae

  • Leaf arrangement: rolled in bud

  • Hair surface: no hairs; hairs on basal half only

  • Ligule: membrane

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

  • Root structure: fibrous

  • Seed head: multiple spikes

  • Width: 6 to 15 mm; less than 5 mm

  • Grass stem: flat or oval