Lawn Weeds in North Texas & When to Treat Them

Yard Smarts guide

The crabgrass you get in June was decided in February

A pre-emergent herbicide does one thing: it stops seeds germinating. It puts a barrier in the top of the soil, and a seed that tries to come up through it fails. What it cannot do is anything at all to a plant that is already growing.

That single fact decides almost everything about weed control here. Crabgrass germinates in North Texas around the beginning of March, when soil temperature in the top inch or two holds at roughly 50 to 55°F for several days running. So the spring application has to be down and watered in during the second half of February or the first days of March — ahead of it, not on top of it.

The two mistakes we see constantly are putting pre-emergent down in April, by which point the decision has already been made for you, and skipping the autumn application entirely. The autumn one is the reason your neighbour’s lawn is not purple with henbit in February.

Soil temperature, not the calendar.

A warm February and a cold one are not the same year. A cheap soil thermometer pushed two inches into the lawn, read mid-morning for several days running, will tell you more than any date we could print. The dates below are what those temperatures usually mean in the Dallas–Fort Worth area — treat them as a guide, not a rule.

Established lawn along a fence line in North Texas

The distinction that decides everything

Annual or perennial?

Before you buy anything, work out which of these three groups you are dealing with. It changes the product, the timing and whether the job is even possible this year.

Summer annuals

Grow from seed every spring, set seed, and die at the first frost. Crabgrass and spurge are the ones you will meet. Pre-emergent in late winter is exactly the right tool, and it works well.

Winter annuals

Germinate in autumn as the soil cools back to about 70°F, sit small through winter, then flower in late winter and die out in the heat. Annual bluegrass, rescuegrass, henbit, chickweed. The autumn application is the whole game.

Perennials

Come back from roots, rhizomes and tubers rather than from seed — dallisgrass, nutsedge, Virginia buttonweed, clover. Pre-emergent does nothing to them at any rate, in any season. These need post-emergent work, usually more than once.

The most expensive misunderstanding in North Texas lawns is calling dallisgrass “crabgrass”. Dallisgrass is perennial. Someone who mixes the two applies pre-emergent faithfully every February, watches the same clumps come back from the same rhizomes in the same spots, and concludes the product does not work. It worked fine. It was aimed at a weed that was not there.

The year

What goes down, and when

Timing is driven by soil temperature and conditions. The dates are what those conditions usually mean in the Dallas–Fort Worth area in an ordinary year.
When	What goes down	Why then
Mid-February to early March	Spring pre-emergent	Crabgrass germinates in North Texas around early March. Pre-emergent has to be down and watered in before that, not on the day it happens. The trigger is soil temperature holding around 50–55°F in the top inch or two for several days running.
Spring, once days are 60–85°F	Broadleaf post-emergent	Below about 60°F broadleaf products simply do not work. Above 85°F you risk injuring hybrid bermuda. That leaves a real but narrow window.
Summer	Spot treatment only	Heat plus herbicide is how lawns get damaged. Correct mowing height and a sensible watering schedule do more for weed pressure in July than anything in a sprayer.
Late August through September	Autumn pre-emergent	As soil temperatures fall back to about 70°F. This is the application almost everybody skips, and it is the one that decides whether you get annual bluegrass, rescuegrass, henbit and chickweed in February.
Autumn, while days are still 60–85°F	Broadleaf post-emergent	The best window of the year for perennial broadleaf weeds — they are moving resources down into their roots, and they take the product with them.
Winter	Largely nothing	Broadleaf products are ineffective below about 60°F. Winter weeds visible in February were settled the previous autumn; spraying them then is damage limitation, not control.

Pre-emergent has to be watered in, or it does nothing.

Granular products need roughly a quarter to half an inch of water to move off the granule and into the top of the soil, and that has to happen before the weeds germinate rather than after. On blackland clay, a half inch applied in one run will largely end up in the street — split it into two shorter cycles with an hour between them. Same principle as everything else you water here. The DFW watering guide →

Identification

What is actually growing in your lawn

Grouped by what they are, because that is what determines whether you can do anything about them this year.

The common ones. If you have something here that does not match any of these, take a close photo including the base of the plant — identification usually comes down to the stem and the seedhead, not the leaf.
Weed	How to know it	Why it matters
Summer annuals — grow from seed every year
Crabgrass	Hairy leaf sheaths and blades. The seedhead branches radiate out from a single point like fingers. Spreads by rooting wherever a stem touches the ground.	The entire reason for the February application. Once it is up and growing, pre-emergent will not touch it.
Spotted spurge	A flat mat, usually along pavement edges and wherever the turf is thin. Break a stem and it bleeds milky white sap — nothing else in a North Texas lawn does that.	It is telling you the turf is thin there. Thickening the lawn does more than spraying it.
Winter annuals — germinate in autumn, show up in February
Annual bluegrass (poa annua)	Lighter yellow-green than the lawn around it. The leaf tip is shaped like the front of a boat. It produces seedheads even when mown very short.	If something is making seedheads below your mower height, it is poa annua. An autumn pre-emergent is the only easy answer; by February it is too late for that year.
Rescuegrass	Coarse and very conspicuous against dormant winter bermuda. Drooping seedhead with strongly flattened spikelets.	Same autumn window, same answer as annual bluegrass.
Henbit	Square stems — roll one between your fingers. Leaves clasp the stem, and whorls of pinkish-purple flowers open in late winter.	The purple haze across North Texas lawns every February. It was decided the previous September.
Chickweed	Low and spreading, leaves in opposite pairs, small white flowers, largely smooth stems.	Same window and same answer as henbit. Both are winter annuals that die out on their own in the heat — the question is only whether you want to look at them until then.
Perennials — pre-emergent will not touch these
Dallisgrass	Coarse clumps. The seedhead branches are spaced out along a central stalk rather than radiating from one point the way crabgrass does. Comes back from deep rhizomes, in the same spot, year after year.	Constantly mistaken for crabgrass. That single mistake costs people a pre-emergent application every February that was never going to work, and then a bad opinion of the product.
Nutsedge (yellow and purple)	Not a grass at all. Roll a stem between your fingers and it is triangular. Leaves come off the stem in three rows rather than two. It grows faster than turf, so it stands proud a couple of days after you mow.	It regrows from underground tubers, not from seed, so a pre-emergent barrier does nothing to it. A patch that returns in the same place every year is usually telling you that spot stays wet.
Virginia buttonweed	Sprawling stems that root where they touch the ground, and small white flowers with four petals.	Perennial, so it defeats pre-emergent for exactly the same reason dallisgrass does.
White clover	Three leaflets, each usually carrying a pale crescent mark. White flower heads.	Clover fixes its own nitrogen, so it wins wherever the lawn is underfed. Clover across a whole lawn is usually a fertility message rather than a weed problem.

Nutsedge that comes back in the same spot is a drainage message.

Nutsedge favours ground that stays wet. A patch that returns to the same corner every summer, no matter what you spray, is usually sitting on a low spot, a broken head or a line that leaks. Fix that and the sedge gets a lot easier. Standing water and drainage →

Read this before you buy anything

Six ways people damage their own lawn

Quinclorac on St. Augustine

Quinclorac is the crabgrass ingredient in a lot of all-in-one bags, and its label says plainly not to apply it to St. Augustinegrass. A homeowner treating crabgrass in a St. Augustine lawn with the wrong bag can do more damage than the crabgrass was ever going to.

Broadcasting atrazine

Atrazine is marketed at St. Augustine owners, but the label prohibits it for winter weed control on St. Augustine, injury is very likely on bermudagrass, and under the current federal decision its use on landscape turf is restricted to spot treatment. People routinely spread it across a whole lawn.

2,4-D on the wrong grass

Injury is more likely on St. Augustine, buffalograss and centipede than on bermuda. A product that is completely safe on your neighbour’s bermuda lawn is not automatically safe on yours.

Spraying in the heat

Broadleaf herbicides do not work below about 60°F, and should not go on hybrid bermuda above 85°F. In this climate that leaves spring and autumn. Spraying broadleaf weeds in a Dallas July is both ineffective and risky.

Pre-emergent, then new grass

A pre-emergent barrier cannot tell weed seed from turf seed. If you are overseeding, laying sod or repairing bare ground, check the label first — many products are labelled for established turf only, and seeded or sprigged areas may not count as established for the best part of a year.

Spraying just before rain

Rain washes product off the site and into the storm drain instead of into the soil or the leaf. You lose the application and it ends up in a creek. Check the forecast, not just the temperature.

If you find older advice recommending MSMA for dallisgrass, ignore it. That use was cancelled for residential lawns years ago and survives only for golf courses, sod farms and highway rights-of-way. Some perfectly reputable publications still carry it because they were written for professional turf managers rather than homeowners.

Maintained lawn in front of a North Texas home

The free one

Mowing height is the cheapest weed control you own

Crabgrass and spurge seed needs light at the soil surface to germinate. A taller cut shades that surface; scalping exposes it. Extension guidance says this outright — mowing higher shades out weeds, and cutting too short increases weed encroachment by letting sunlight reach the soil.

It also gets you deeper roots and better water infiltration, which on clay is worth having on its own. And it costs nothing.

Whatever the grass, never take off more than a third of the leaf in one cut. If it has got away from you, bring it down over two or three mowings rather than one.
Grass	Mowing height	Note
Bermudagrass	1 to 2 inches	With a rotary mower. Hybrid varieties sit at the lower end.
St. Augustinegrass	2½ to 3 inches	Cutting St. Augustine short is one of the most common self-inflicted lawn problems here.
Zoysiagrass	½ to 2 inches	Varies a lot by variety — the fine-bladed types want an inch or less.
Buffalograss	2½ to 3 inches	Low input by nature; it does not want much attention.
Tall fescue	2 inches, raised to 3	Raise it to about 3 inches in heavy shade and through summer heat.

What weeds do and do not tell you

Reading the lawn

There is a persistent idea that each weed diagnoses a specific soil problem — dandelions mean compaction, and so on. It is half true, and the half that is false gets people spending money on the wrong thing.

Two associations do hold up well enough to act on. Clover across a whole lawn genuinely does suggest the turf is short of nitrogen, because clover makes its own and therefore competes best where the grass is underfed. Nutsedge concentrated in one area genuinely does suggest that area stays wetter than the rest — a low spot, a leak, or somewhere the irrigation overlaps twice.

Beyond those, most weeds grow perfectly happily across a wide range of conditions, and a single species is not a diagnosis. Treat a weed as a prompt to go and look at something, not as an answer. On blackland clay a soil test is worth doing anyway, and it costs less than one wasted bag of the wrong product.

If you hire it out

Ask to see the licence

In Texas, applying any pesticide to someone else’s property for hire requires a licence from the Texas Department of Agriculture. That includes general-use products you could buy off a shelf yourself — the trigger is being paid, not the strength of the chemical. A company spraying consumer-grade weed killer on your lawn for money still needs to be licensed.

Ask for it, exactly as you would ask an irrigation contractor for their TCEQ number. Anyone legitimate will show you without hesitating.

The reason it matters is not paperwork. It is that a licensed program is built around what the turf needs, at label rate, at the right time of year — rather than a blanket application of whatever was in the truck.

Our chemical application services

Planting beds and turf edge on a North Texas property

Rather not think about the calendar?

A licensed program timed to soil conditions, on a schedule, so the February application actually happens in February.

Get an Estimate Call (972) 240-8082

FAQs

Weed questions we get asked

I put pre-emergent down and still got weeds. Why?

Three usual reasons. It went down too late, after germination had already started. It was never watered in, so it stayed on the surface. Or the weed you are looking at is a perennial like dallisgrass or nutsedge, which comes back from roots and tubers rather than from seed and was never going to be affected.

How do I tell crabgrass from dallisgrass?

Look at the seedhead. Crabgrass branches radiate from a single point like fingers; dallisgrass branches are spaced out along a central stalk. The other tell is history — dallisgrass is perennial, so it returns to the same clumps in the same spots year after year. Crabgrass comes up wherever seed happened to land.

What is the weed that stands up a day after I mow?

Almost certainly nutsedge. Roll a stem between your fingers: sedges have triangular stems where grasses are round. It grows faster than turf, which is why it is visible again so quickly. It regrows from tubers, so pre-emergent does nothing and it needs a product specifically labelled for sedges.

Is clover actually a problem?

Not necessarily. It is a legume, it fixes its own nitrogen, and bees like it. But a lawn that is mostly clover is usually a lawn that is short of nitrogen — so if you want it gone, feeding the grass properly does more of the work than spraying does.

Can I just use one product for everything?

Not safely. Products that are fine on bermuda can injure St. Augustine, buffalograss and centipede, and the temperature windows for pre-emergent and broadleaf work do not overlap. Knowing which grass you have is the first step, and it is worth being certain rather than assuming.

When exactly should I put down pre-emergent in Dallas or Rockwall?

Roughly mid-February to the first days of March for the spring application, and late August through September for the autumn one — but drive it off soil temperature rather than the date. Around 50 to 55°F and rising in spring, around 70°F and falling in autumn, held for several days in a row.

Do I need a licensed applicator?

Only if you are paying someone. Treating your own lawn needs no licence. Anyone you hire to apply pesticides to your property does need one from the Texas Department of Agriculture, including for general-use products.

Let’s talk

Get an estimate

Tell us about the lawn and what is coming up in it. We’ll follow up to discuss a program.

Prefer to talk? Call (972) 240-8082, Monday to Friday, 8:00 AM to 5:00 PM.

Lawn Weeds & When to Treat

The crabgrass you get in June was decided in February

Annual or perennial?

Summer annuals

Winter annuals

Perennials

What goes down, and when

What is actually growing in your lawn

Six ways people damage their own lawn

Quinclorac on St. Augustine

Broadcasting atrazine

2,4-D on the wrong grass

Spraying in the heat

Pre-emergent, then new grass

Spraying just before rain

Mowing height is the cheapest weed control you own

Reading the lawn

Ask to see the licence

Rather not think about the calendar?

Weed questions we get asked

Get an estimate