Dallisgrass Control in Missouri Lawns: Identification, Prevention, and Removal

If you have clumps of thick, coarse grass showing up in your St. Charles County lawn this month — especially in spots where the fescue is thinning — there is a good chance you are dealing with dallisgrass.

Dallisgrass is a warm-season perennial grassy weed that stands out in July because it grows faster and coarser than your tall fescue. It forms distinct clumps that get taller and wider as summer goes on, and it is one of the harder weeds to get rid of.

Here is how to identify it, why it is so stubborn, and what your options are for controlling it.

What Is Dallisgrass?

Dallisgrass (Paspalum dilatatum) is a perennial bunch-type grass native to South America. It was introduced to the United States decades ago as a forage grass, but it spread beyond pasture land and is now a common weed in lawns across the southern and transition zone — including Missouri.

Unlike annual grassy weeds like crabgrass that die off each winter, dallisgrass comes back year after year from the same root system. That is the first reason it is harder to control.

It grows actively from late spring through early fall, which means July and August are prime time for it to spread and set seed.

Dallisgrass vs. Crabgrass: How to Tell the Difference

This is the most common ID question I get. Both are grassy weeds that show up in summer, but they look different up close and they require different approaches.

Feature	Dallisgrass	Crabgrass
Growth habit	Distinct clumps that grow outward in circles	Low, spreading mats that hug the ground
Leaf texture	Coarse, wide blades with a prominent midrib	Slightly finer blades, often lighter green
Seed heads	Tall, purple-tinged spikes with multiple branches	”Crab leg” fingers at the top of stems
Life cycle	Perennial — comes back every year	Annual — dies each winter, regrows from seed
Root system	Deep, thick rhizomes	Shallow, fibrous roots
Best control timing	Summer (spot treatment) or fall renovation	Spring pre-emergent or early post-emergent

If you have a clump of coarse grass that keeps getting bigger every year and feels thicker than the rest of your lawn, it is probably dallisgrass. Crabgrass spreads low and wide — dallisgrass makes tall, lumpy clumps.

Why Dallisgrass Is So Hard to Control

There are three main reasons dallisgrass is tougher than most summer weeds.

First, it is perennial. It survives winter and comes back from the same root system. A single clump that was there last year will be back this year, often bigger.

Second, the seed can stay viable in the soil for years. Even after you kill existing plants, dormant seeds can germinate later. This is why dallisgrass can seem to appear out of nowhere in a lawn that looked fine the year before.

Third, the seed heads grow fast. Dallisgrass grows noticeably faster than tall fescue. Between mowings, it can shoot up a seed head and drop new seeds into your lawn before you even notice. By the time you see the seed head, it may have already spread.

Cultural Control: Mowing and Lawn Density

Because dallisgrass is so hard to kill with herbicides alone, cultural practices matter more than usual. The goal is to make your lawn thick and healthy enough to crowd it out while preventing new seeds from dropping.

Mow high and mow often. Keep your mower at 3.5 to 4 inches during summer. A taller canopy shades the soil and makes it harder for dallisgrass seedlings to establish. And because dallisgrass grows fast, mowing every 4 to 5 days instead of once a week can keep it from producing seed heads between cuts.

Bag the clippings if you have dallisgrass going to seed. Normally I recommend leaving clippings on the lawn, but if dallisgrass seed heads are present, bagging removes them before they can drop seed.

Thicken the lawn in fall. The best long-term defense against dallisgrass is a dense stand of tall fescue. Fall aeration and overseeding give your fescue the advantage it needs to fill in thin spots that dallisgrass would otherwise take over.

Chemical Control Options

There is no easy one-and-done spray for dallisgrass. You need persistence and the right product for your grass type.

Spot Treatment in Fescue Lawns

For dallisgrass in tall fescue or Kentucky bluegrass, the most effective approach is spot treatment with a selective herbicide containing quinclorac or fenoxaprop. These are post-emergent grassy weed herbicides that can suppress or kill dallisgrass with repeat applications.

Apply during active growth — right now, in July, is good timing. The weed needs to be growing vigorously for the herbicide to work.

What to expect: One application rarely kills dallisgrass completely. Plan on 2 to 3 applications spaced 3 to 4 weeks apart. The clump will weaken with each treatment but may not disappear entirely until fall.

Important: Read the label carefully. Make sure the product is labeled for use on tall fescue lawns. Some grassy weed killers will damage cool-season turf if applied at the wrong rate or temperature.

What About Pre-Emergent?

Standard spring pre-emergent applications for crabgrass (prodiamine, dithiopyr, pendimethalin) have limited effect on dallisgrass. The seeds are more resilient and can germinate even when pre-emergent is present. Do not rely on pre-emergent alone for dallisgrass.

When Over-the-Counter Products Fall Short

Many over-the-counter weed killers do not work well on dallisgrass. Studies from university turf programs have shown that some products sold at big-box stores do not provide reliable control, especially on established clumps.

If you have tried spot treatment twice and the dallisgrass is still spreading, it may be time to call a licensed lawn care provider. They have access to professional-grade products — including ones with active ingredients like sulfosulfuron or fluazifop — that are not available to homeowners.

Mechanical Removal

For a small number of clumps — fewer than a dozen — hand-digging is a reasonable option. But you have to get the whole root system.

Use a dandelion digger or a narrow trowel. Dig down several inches around the clump and try to lift the entire root mass. Dallisgrass roots can go deeper than you expect, and any piece left behind can regrow.

After digging, fill the hole with topsoil and seed with tall fescue in the fall. Do not try to seed bare spots in July — the heat will kill new seedlings. Mark the spots and overseed in September.

Dallisgrass in Bermuda or Zoysia Lawns

If you have a warm-season lawn like bermudagrass or zoysia, the options are different. Certain selective herbicides that would damage fescue (like fluazifop) can be used safely on bermudagrass. A lawn care provider can match the right product to your grass type.

When to Call a Professional

Dallisgrass is one of those weeds where DIY can work, but only if you catch it early and stay consistent. If dallisgrass is scattered across a large area — more than a dozen clumps — or if you have tried spot treatments with no improvement, bringing in a licensed applicator is usually the faster path.

A provider can do a thorough evaluation, apply professional-grade products, and set up a treatment schedule that runs through the rest of summer and into fall.

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Bottom line: Dallisgrass does not go away on its own. But with consistent mowing, spot treatment, and a solid fall overseeding plan, you can get it under control. If you want help comparing local lawn care options, that is what Midwest Lawn Care is here for.

Request Local Lawn Care Help

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Last updated: July 2026. Parts of this article reference MU Extension publications on turfgrass weed management.