Dallisgrass

What is dallisgrass?

Dallisgrass is a warm-season perennial bunchgrass from South America that was introduced to the United States in the 1800s for forage and is now naturalized across much of the South. dallisgrass identification usually starts with the clumps: coarse, grayish blades that stand out against finer turf, and seed stalks that slip under the mower and then shoot up above the lawn.

It builds solid, lumpy clumps that spoil a smooth lawn or sports field and can trip people. It grows faster than most turfgrasses, tolerates low mowing and responds strongly to nitrogen, and Extension specialists rank it among the hardest grassy turf weeds to control; clearing an established stand usually takes two to three years. In pastures, an ergot fungus on its seed heads can poison grazing animals.

Dallisgrass identification: what to look for

Look at a clump at ground level, then dig one up. Its blades are wider and duller than crabgrass, its seed branches droop, and it comes back from the same spot every year. The short, ring-jointed rhizomes at the base settle it.

• Clumps: Loose bunches that widen slowly from the edges. Older clumps can die out in the center and fill in with other plants.
• Leaves: Coarse, gray-green blades roughly 1/4 to 1/2 inch wide with a strong midrib, 4 to 10 inches long if unmowed. Leaves are rolled in the bud, and the color is duller than crabgrass.
• Ligule and collar: A membranous ligule up to about 1/4 inch tall where the blade meets the sheath, no auricles, and often a few long hairs along the collar edges and near the base of the plant.
• Stem base: Leaf sheaths are somewhat flattened and often purplish near the ground.
• Seed head: A stalk 1 to 5 feet tall with roughly 2 to 10 drooping branches arranged alternately near the top. Each branch carries rows of small, flat, egg-shaped spikelets fringed with fine hairs, pale green to purple.
• Rhizomes: Very short and shallow, with closely spaced joints that look like concentric rings. This is the best way to separate it from crabgrass.

Where it grows in the United States

Dallisgrass is naturalized across much of the southern United States, where it was once planted for pasture, and it remains common in southern pastures, hay fields and roadsides. In Arkansas it is most common in the southern half of the state on low, moist soils, and in California it grows nearly statewide outside the Great Basin and Sonoran Desert regions. USDA lists it as introduced in the lower 48 states, Hawaii and Puerto Rico.

Its favorite places are wet: drainage ditches, wet roadsides, low spots and heavily irrigated turf. It also turns up in orchards, vineyards, landscape beds and low-maintenance lawns with erratic watering. It handles sandy or heavy clay soils and, once established, both drought and frost. Seed moves in runoff and on mowers, people and pets, which is how it jumps from ditches into nearby lawns.

Dallisgrass look-alikes

A few plants get mixed up with it:

• Crabgrass (Digitaria spp.): Leaves look similar, but crabgrass is a brighter green and lacks the short, ring-jointed rhizomes at the base of a dallisgrass clump. Dallisgrass also has larger seed stalks and seeds.
• Field paspalum and thin paspalum (Paspalum laeve, Paspalum setaceum): Close relatives that are often misidentified as dallisgrass, and all three are stubborn perennial turf weeds. Young thin paspalum leaves are glossier than dallisgrass.
• Knotgrass (Paspalum distichum): A related perennial that spreads into low mats, while dallisgrass grows in distinct clumps.

How to get rid of dallisgrass

Pulling, digging and mowing: Mowing will not remove it; persistent digging will. Dig young plants before they form rhizomes or set seed, and take the whole crown on mature clumps, because leftover rhizome regrows. In rough areas such as fence lines, dig clumps in summer and leave them turned over to dry completely; fully dried rhizomes do not come back. In beds, remove plants with their rhizomes and lay a thick mulch, or cut large stands to the soil and cover them with black plastic or landscape fabric. Summer solarization under clear plastic also cuts seed and rhizome survival.

Cultural control matters most, because the right conditions keep it from coming back.

• Mow at the right height for your grass and keep fertility and watering on track so the turf stays dense with no open gaps.
• Overseed or sod bare patches right after removing clumps so new seedlings have no room.
• Fix wet, soggy or overwatered areas, which favor dallisgrass.
• In an infested lawn, hold off on spring core aeration, which opens gaps just as seedlings are sprouting.
• In pastures, clip seed heads in late summer so livestock cannot graze ergot-infected heads.

Herbicides: Control has to hit both established clumps and seed, and usually takes two to three years. For seedlings, apply a preemergence herbicide in late winter or early spring; crabgrass products with active ingredients such as benefin, bensulide, dithiopyr, oryzalin, pendimethalin, prodiamine or trifluralin generally work on dallisgrass too. Established clumps in warm-season lawns call for sulfonylurea herbicides such as foramsulfuron, thiencarbazone-methyl, trifloxysulfuron and sulfosulfuron. University of California recommends at least three treatments: one in fall when air temperatures drop to about 70°F, another four to six weeks later, and a third in mid- to late spring as growth resumes; starting in late spring or summer works less well. Spot-treat rather than broadcast, and avoid leaning on the same sulfonylurea year after year, since that can lead to resistance. These products injure cool-season grasses; in tall and fine fescue, fluazifop is the main selective option, used in spring or fall rather than midsummer. Glyphosate spot treatment kills the turf too, so plan to replant. Many of these products are restricted to licensed applicators. Use products labeled for your turf species and site, and follow the label, which is the law. If you hire someone to spray, make sure they hold your state’s pesticide applicator license; the rules for each state are in our pesticide applicator license guide.

Keeping it from coming back

Dallisgrass mostly arrives as seed carried by water, mowers, sod and fill soil. Clean your mower after cutting an infested area, look sod over before it is laid, never fill low spots with soil from an infested site, and dig young plants before they seed.

Long term, a dense lawn is the best defense: keep mowing, fertility and irrigation right for your grass, fill thin spots quickly, skip spring aeration in infested lawns while seedlings are sprouting, and drain wet, low areas.

Questions we get about dallisgrass

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