Dallisgrass

The coarse, blue-green clump-grass that throws up tall seed stalks days after you mow — always in the same wet, sunny, beaten-down low spots. It's Paspalum dilatatum, a warm-season perennial, and that word is the whole problem: unlike the stiltgrass, you can't just pull it. It regrows from a woody crown, and there's no selective spray that takes it out of a cool-season lawn without killing the lawn too. So this one is about spot, reseed, and fix the ground.

Also called

Dallies, Paspalum dilatatum

Type

Warm-season perennial grass — clumping, short knobby rhizomes

Loves

Full sun · wet / poorly-drained low spots · compacted, fertile ground

Spreads by

Seed (mower, water, birds) and its own expanding crown

01What you're looking at

Expanding coarse clumps, and a seed stalk you can't mow away.

A coarse, greyish-blue-green grass growing in distinct circular clumps that widen outward year on year, often into a ring with a tired middle. The blades are wide and flat with a rough edge, and the plant grows from a short, knobby crown of stubby rhizomes — that crown is why hand-pulling fails and why it comes back every summer. The dead giveaway is the seedhead: a tall stalk carrying three to seven finger-like spikes branching off a central stem, the seeds set in neat rows and often flecked with sticky black ergot. It outruns your turf, so those ugly stalks reappear days after mowing. Where it's winning it's reading you the ground's story — not the clover's baked, starved soil, but the opposite: sun, wet feet, and compaction. Kill the plant now; fix the drainage over time.

Compare the shade-and-damp invader: Japanese stiltgrass · and the sun-and-compaction one: Japanese clover.

02Knock it back now

There's no easy selective — spot-kill, dig, and reseed the hole.

• Spot-kill established clumps with glyphosate. In a cool-season lawn (fescue, bluegrass, rye) nothing selective reliably takes dallisgrass out, so the honest tool is a non-selective glyphosate spot-spray on each clump — accepting it kills a coin of surrounding turf too. Paint or spot-spray the clump, wait for full brown-out (2–3 weeks), and expect to hit stubborn crowns a second time — the short rhizomes survive one light pass. See Glyphosate Plus.
• Dig out the small ones — get the whole crown. For a handful of young clumps it's faster to cut them out with a spade than to spray. It's a perennial, so you must lift the entire woody crown and its stubby rhizomes — leave a chunk and it re-sprouts. Bag any plant already carrying seedheads instead of composting it.
• Reseed the bare spot straight away. Every kill or dig leaves an opening, and bare ground is exactly what dallisgrass (and crabgrass) recolonise. Rough up the dead patch, drop cool-season seed, and keep it damp — a thick stand is the only lasting selective you've got against it.
• MSMA — only where it's still legal. The old professional answer for dallisgrass was the arsenical MSMA, which is genuinely the one chemistry that hits it hard — but it's now restricted to golf, sod farms and roadsides in most states and is not for residential lawns. If you're a licensed applicator on an allowed site, it takes repeat apps. Full detail and the restrictions: MSMA 6 Plus.

03Stop it coming back

Fix the ground that invites it, then deny the seed.

• This seasonFix the wet, compacted low spots. Dallisgrass thrives where turf struggles — standing water, hardpan, worn tracks. Core-aerate the compaction, and re-grade or drain the puddling areas. Take away the wet-and-beaten conditions and you take away its edge.
• Next springPre-emergent for the seedlings. A spring prodiamine or dithiopyr pre-emergent won't touch an established perennial crown, but it stops the seed from germinating — cutting off next year's new plants while you deal with the old ones. Time it with the seasonal calendar.
• Every mowMow high, never scalp. Cut cool-season turf tall (3–4 in) so it shades the soil surface — dallisgrass seed needs light and open ground to establish. Scalping and bare patches hand it the opening.
• OngoingThicken the stand. The single best long-term control of a perennial weed-grass is a dense, well-fed lawn with no gaps. Overseed thin areas each fall so there's simply nowhere for a new clump to start.

04If it comes back next summer

Expect it — perennial crown plus seed bank means it plays a long game.

Because dallisgrass survives as a perennial crown and reloads from seed, a fresh clump or two next summer isn't failure — it's the same fight, not a lost one. The plant itself is beatable one clump at a time; what keeps it in the yard is open, wet, compacted ground. Keep spot-killing and digging, keep reseeding every hole, keep the low spots draining and the turf thick, and each season there's less bare ground for it to claim.