Dallisgrass

Dallisgrass (Paspalum dilatatum) is a clump-forming warm-season perennial grass that grows in coarse, expanding circular tufts. Blades are wide and flat (about a quarter to a half inch), light to medium green, with a rough texture and a prominent whitish midrib. The plant spreads outward from short, thick rhizomes at the base of the clump. Its most diagnostic feature is the seedhead: a tall flowering stalk one to five feet high bearing two to ten finger-like, often drooping branches arranged alternately along the stalk, with each branch carrying paired rows of flat, egg-shaped seeds fringed with silky hairs. The coarse clumping habit and the short basal rhizomes help separate dallisgrass from crabgrass (a prostrate annual) and from bahiagrass, which has a distinctive Y-shaped seedhead.

Dallisgrass degrades turf by forming coarse, fast-growing clumps that contrast sharply in color and texture with finer turfgrasses, creating an uneven, patchy surface. The clumps grow faster than surrounding turf so they appear as tall tufts between mowings and disrupt playability and uniformity on lawns and sports fields. As clumps enlarge they crowd out desirable grass, and the tall seedheads further mar appearance and reseed the area, while dead winter clumps leave open spots.

Dallisgrass is a warm-season perennial that survives from year to year by short, knotty rhizomes and reproduces both by seed and by vegetative spread. Seedlings germinate in spring as soil temperatures reach roughly 60 to 65 degrees F, and the plant grows most rapidly when air temperatures are in the 80 to 90 degree F range. Established clumps expand outward by the short rhizomes and produce abundant seed through summer and fall, making the perennial crown and rhizome system the persistent structures that drive its difficulty to control.

Dallisgrass thrives in moist, fertile sites and is frequently found in drainage ditches, low spots, and heavily or frequently irrigated turf. It invades thin, scalped, or stressed stands where competition is reduced and is favored by warm summer conditions and overwatering. Once a clump establishes, the perennial rhizome system lets it persist and enlarge season after season, with new plants also recruiting from its prolific seed.