Dallisgrass vs Crabgrass: One Comes Back Every Year

Two grassy weeds, nearly identical at a glance, requiring opposite strategies. Mistaking one for the other is why some people spray the same patch for three summers and never win: they are applying an annual-weed playbook to a perennial plant.

The Four Checks That Settle It

Work down this list. Any single one is usually decisive.

1. Growth habit — the fastest tell

Crabgrass sprawls. Blades radiate outward from one central point in a low fan or star, pressed close to the ground, and stems often root where they contact soil.

Dallisgrass stands up. It forms a tight, upright clump — a distinct tuft that sits noticeably above the mow line rather than spreading sideways.

2. The base of the plant

This is the definitive check. Part the blades and look at where they meet the soil.

Crabgrass has a soft, fibrous crown you can pull apart with your fingers.

Dallisgrass has a thick, woody, almost knotted crown — a perennial structure that stores energy through winter, often with short rhizomes radiating from it. It resists pulling, and if you do pull it, it tends to break rather than lift.

3. Does it return to the same footprint?

Crabgrass cannot. Every plant dies at frost and next year’s plants grow from scattered seed, so the pattern moves around the lawn.

Dallisgrass does. The same clump regrows from the same crown, in the same place, for years. This history question alone identifies it in most yards.

4. Seedheads

Crabgrass produces several finger-like spikes radiating from one point at the top of a stem.

Dallisgrass sends up taller seed stalks bearing sparse paired branches, often with small dark spots visible on the seed, and it produces them persistently through the season even in mown turf.

For sorting any lawn weed into its family first, start with the weed identification guide. And if you want to check your plant against a photograph rather than a description, Texas A&M AgriLife’s Weeds of Texas Turf gallery is a photo reference for turf weeds — identification only, which is the right tool for this step.

New Mexico Lawn Threat Matrix

What to scout for on Bermuda lawns in USDA zones 4b–9a.

High-Risk Weeds

• Crabgrass in irrigated turf
• Puncturevine — goathead, the signature southwestern hot-dry-ground annual and a tyre and bare-foot problem as much as a turf one
• Field bindweed
• Kochia and Russian thistle at the dry margins
• Khakiweed and spurges in thin, hot, compacted ground
• Bermudagrass encroaching into a northern bluegrass lawn, which is the transition zone working against you
• Annual bluegrass (Poa annua) in over-irrigated cool-season turf

High-Risk Diseases

• Iron chlorosis — not a pathogen, but the most common reason a New Mexico lawn is yellow, and the one where buying the wrong chelate wastes the money entirely
• Salinity injury from irrigation water and from salts accumulating above caliche, which reads as drought stress that watering does not fix
• Spring dead spot on bermudagrass, appearing as the lawn greens up
• Summer patch and other root-zone diseases on cool-season lawns in the north
• Dollar spot
• Large patch on zoysia as soil passes through the 70s

Common Pests

• White grubs from May and June beetles and masked chafer
• Chinch bugs in hot dry sandy strips, which describes most of the state
• Bermudagrass mites in the south
• Sod webworm
• Cutworms and armyworms in monsoon years
• Bluegrass billbug in the northern cool-season lawns
• Red imported fire ants in isolated instances only, with Dona Ana County under quarantine: nursery stock, sod, soil, baled hay and straw, and soil-moving equipment leaving the county must be certified free of the pest

Regional relevance: dallisgrass is not among New Mexico's top documented weeds, so crabgrass is the more probable answer — but check the crown anyway, because the treatment paths diverge completely. Both compete hardest where Bermuda has thinned.

Why the Difference Changes Everything

The annual-versus-perennial distinction determines which tools can work at all.

The practical consequence: a pre-emergent program that eliminates crabgrass from a lawn in two or three seasons will leave a dallisgrass clump completely untouched. If you have been “winning against everything except that one patch,” that patch is the perennial.

Why these two do well in New Mexico specifically: your soils are Calcareous desert soils across the basins and mesas, with caliche — a cemented lime hardpan — at shallow depth in much of the state; deeper alluvium along the Rio Grande and the river valleys, and drainage reads: Fast through the sandy desert soils until it reaches caliche, at which point it stops — a shallow lime pan perches water, blocks roots and turns a deep watering into a shallow one, so the depth to caliche matters more here than the surface texture does. Fast drainage dries the surface between waterings and thins the canopy, and both of these weeds establish in exactly those gaps — deep, infrequent irrigation and a taller cut do more for you here than any extra spray.

Treating Dallisgrass, Honestly

This is where most lawn content oversells, so here is the straight version.

The product that used to be the answer is gone. Maryland Extension states it plainly: “Herbicides that contain MSMA and DSMA, which were classically used to control Dallisgrass, are no longer labeled to be used on home turf.” Remaining registrations are limited to professional settings such as golf courses and sod production, so any advice that still recommends MSMA for your yard is out of date.

What is realistically available to a homeowner:

1. Repeat quinclorac applications. Products containing quinclorac suppress dallisgrass with mixed and often modest results. Expect several applications across a season, spaced per the label, and expect regrowth from the crown.

2. Excavation for isolated clumps. For a handful of plants this is the most reliable route. Dig several inches wider and deeper than the clump to remove the entire crown and surrounding rhizomes, then refill and replant.

3. Spot-kill and renovate. For heavier infestations: treat the clumps with a non-selective herbicide, confirm a complete kill, observe the label’s replant interval, then re-establish turf.

   Be clear about where that last one comes from, because we would rather you knew. NC State’s dallisgrass publication does not publish it — their page says only that “selective control measures are usually difficult” and points at prevention: “maintaining a dense, healthy turf year round by proper mowing and fertilization helps prevent encroachment and weed establishment.” Spot-killing is what is left once the selective options are ruled out, and it is the same route quackgrass takes for the same reason — including the wiped rather than sprayed application that keeps the surrounding lawn alive. It is a reasonable inference, not a recommendation we can hand you someone else’s name for.

Nothing here is a one-application fix for established dallisgrass. Anyone promising that is selling you the pre-ban product or selling you disappointment.

The Frost Test in New Mexico

New Mexico hands you a free identification every year. First frost arrives around Early September in the northern mountains; late October into November in the Mesilla Valley and the southern lowlands — and frost kills crabgrass outright while dallisgrass shrugs it off. Walk the lawn two weeks after that date: any coarse clump still green is dallisgrass, no stem-rolling required.

The ground tilts the odds too. Dallisgrass thrives in heavy, moist soils, and New Mexico's profile — Calcareous desert soils across the basins and mesas, with caliche — a cemented lime hardpan — at shallow depth in much of the state, fast drainage — drains freely enough that crabgrass pressure usually outweighs dallisgrass locally. On Bermuda, that also decides which herbicides the label allows.

Rainfall settles which of the two dominates your lawn. New Mexico rainfall reads: Roughly 8 to 15 inches across most of the populated areas, with a large share of it arriving in the North American monsoon between about June 15 and September 30 as heavy convective storms — which run off caliche and compacted ground rather than soaking in. Humidity: Arid to semi-arid with very low humidity most of the year, broken by the monsoon — and the elevation range means Chama and Las Cruces share almost nothing climatically. Dallisgrass needs sustained moisture to hold its crown through a season, so that steady supply lets it establish well beyond the wet corners — expect it across the lawn, not only in low spots. Soil pH also decides your herbicide options, and here it is alkaline.

Mark those survivors while they are easy to see, because your next moves are seasonal. Fall work here: Cool-season lawns in the north: late August into September is both the seeding window and the most valuable feeding. The spring barrier window that stops the crabgrass half of the problem opens Crabgrass and summer annual pre-emergent as soil holds 55°F at 2 inches — February to early March in the southern valleys, April to May in the north. The state spans two months on this decision. Last frost, for planning repairs, lands around Late May to June at elevation; mid-March in the far south.

Compaction is the shared precondition for both weeds, and relieving it is a separate job with its own timing — see how to aerate your lawn.

Keeping Both Out

Both weeds exploit the same opening: thin turf with light reaching bare soil.

• Never let either set seed. A single season of seed production reloads the seed bank you have been trying to empty.
• Mow at the top of your grass type’s range. On Bermuda, follow the species range rather than a generic number.
• Water deeply and infrequently so turf roots outcompete shallow-rooted invaders.
• Feed on your regional schedule. In New Mexico: New establishment gets 0.5 to 0.75 lb of nitrogen per 1,000 sq ft every other week for six to eight weeks. After that the calendar follows the grass, not the state: cool-season lawns in the north feed spring and autumn, warm-season lawns in the south feed through the warm months and stop well before dormancy.
• Aerate compacted areas annually — both species tolerate compaction better than turf does.
• Scout the same spots each summer. Dallisgrass returns to its footprint, so a photo record of last year’s clumps tells you exactly where to look.

And here is the summer practice your own state's calendar calls for, which is the one most people skip: NMSU's water figures are the ones to plan against: cool-season turf uses about 0.26 to 0.50 inch a day in summer, roughly 1.8 to 3.5 inches a week, and about 38 inches over a year, against about 24 inches for warm-season turf. Getting that right does more against both weeds than an extra herbicide application, because it removes the opening they need.

One tool belongs on that list with an asterisk, and the asterisk is this whole article. A pre-emergent is the strongest thing you can do about crabgrass, because crabgrass is an annual that has to start from seed every year — kill the germination and the plant never exists. It does essentially nothing about established dallisgrass, which is a perennial returning from its own crown and rhizomes rather than from the seed bank. Same granule, same morning, two completely different outcomes.

The window in New Mexico is Crabgrass and summer annual pre-emergent as soil holds 55°F at 2 inches — February to early March in the southern valleys, April to May in the north. The state spans two months on this decision, and that is a soil-temperature condition rather than a date. Dallisgrass is not on New Mexico's own high-risk weed list; the listed pressure is Crabgrass in irrigated turf and Puncturevine. So if you have clumps that survived a pre-emergent, identify before assuming — the four checks above are faster than another application.

Next steps in this cluster: the full annual sequence in our crabgrass guide, and the sedge that fools everyone in how to get rid of nutsedge.

If the perennial has taken enough of the lawn, selective control stops being the answer: Penn State treats the presence of perennial grass weeds as grounds for a kill-off regardless of how much good grass is left. See how to kill a lawn before reseeding.