The Grass-Like Weeds That Take over Southern Lawns in Summer
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Southern lawns deal with some of the sneakiest weeds around — ones that look so much like grass that you can miss them until they've already spread. The most common grassy weeds and grass-like invaders in southern lawns are crabgrass, dallisgrass, yellow nutsedge, goosegrass, signalgrass, carpetgrass, doveweed, and torpedograss. Getting on top of them takes the right identification, the right herbicide, and — honestly — a little patience. This guide covers summer lawn weeds, plus the products that actually work on each one.
Grassy Summer Weeds
If there's one thing that frustrates southern lawn owners more than anything, it's those weeds that look suspiciously like grass. Broadleaf weeds like dandelions, clover, and chickweed are easy enough to spot. But the grass-like stuff? That's where things get sneaky.
Southern lawns deal with a unique lineup of grassy weeds and sedges that love the same heat and humidity your turfgrass does. And because they blend in so well, many homeowners don't realize there’s a problem until those weeds are producing seed heads and spreading across half the yard.
This guide walks you through the identification of the most common southern lawn weeds, what they look like, why they show up, and what you can do about each one.
Why Grassy Weeds Are so Hard to Spot
Most weed guides focus on broadleaf weeds because they're easy to spot. A dandelion doesn't try to hide. But grassy weeds — and their close relatives, the sedges — are sneakier. They germinate as a single leaf and grow blades that look almost identical to your turf. By the time they've spread enough to catch your attention, they've already dropped thousands of seeds.
Your lawn isn't being dramatic when it starts looking patchy in midsummer. It's trying to tell you something — and chances are, a grassy weed is doing the talking.
The key difference between grassy weeds and your desirable southern lawn grasses? Look closely at texture, growth habit, and color. Grassy weeds tend to be coarser, faster-growing, and a slightly different shade of green. Some produce distinctive seed heads that give them away. Others, like nutsedge, have a stem you can actually feel — it's triangular, not round like grass.
Once you know what to look for, these weeds are much easier to catch early.
The 8 Grassy Weeds Causing the Most Trouble in Southern Lawns
1. Crabgrass (Digitaria spp.)
The weed that thrives where your lawn is weakest.
Crabgrass is probably the most well-known grassy weed in southern lawn care for good reason. It's aggressive, prolific, and loves the same conditions that stress your desirable grass: thin turf, compacted soil, and bare spots baking in summer heat.
How to identify it: Crabgrass grows low and outward, with branching stems that sprawl across the soil like — you guessed it — crab legs. The leaf blades are broader and coarser than most southern lawn grasses, and there's often a purplish tint at the base of the stems. When it matures in late summer, it sends up distinctive finger-like seed heads at the top of each stem. One crabgrass plant can produce up to 150,000 seeds before the first frost kills it, which is why getting ahead of it in spring is so important.
Why it shows up: Crabgrass is an annual weed, meaning it germinates from seed every year. It germinates when soil temperatures at 2 inches reach around 55°F for several consecutive days — typically late winter to early spring in the Deep South, and a few weeks later as you move further north. Thin, stressed turf gives it the opening it needs. Once it's established, it's much harder to remove.
How to control it:
Prevention first: A pre-emergent herbicide applied before soil temperatures hit 55°F is your most effective tool. A split application — one in early spring, then follow-up six to eight weeks later — gives you the best season-long coverage.
Already up and growing?: Drive XLR8 (quinclorac) is one of the most effective post-emergent options for crabgrass in warm-season turf — it works on Bermudagrass and Zoysia without damaging your lawn, and handles plants at the two to four-tiller stage well. For timing issues, Dimension (dithiopyr) also offers early post-emergent activity on young seedlings before they tiller.
Prevent it long-term: Thick, healthy turf is your best weapon. Crabgrass can't get a foothold in a dense lawn. Mow at the correct height for your grass type, fertilize on a consistent schedule, and overseed any thin areas in the appropriate season.
2. Dallisgrass (Paspalum dilatatum)
The perennial troublemaker that just keeps coming back.
If you've ever noticed ugly, clumpy tufts of coarse grass poking up above your lawn that seem to grow back no matter how many times you mow — that's almost certainly dallisgrass. It's one of the most stubborn grassy weeds in southern lawns, and it's worth knowing exactly what you're dealing with before you reach for a herbicide.
How to identify it: Dallisgrass grows in a distinct star-shaped or circular clump that expands outward over time. The leaf blades are wider and coarser than those of most desirable southern grasses, and they are gray-green. The real giveaway is the seed head: tall stems with three to five finger-like segments radiating out from a central point, covered in fine, dark spots. Once you've seen it, you won't forget it. It's most aggressive from late spring through October.
Why it's so difficult: Unlike crabgrass, dallisgrass is a perennial weed. It doesn't die off in winter — it goes dormant, then comes right back with a vengeance in the spring. It spreads both by seed and through underground rhizomes (root-like stems), which is why pulling it by hand rarely works. You'll pull the top, but those underground structures stay right where they are.
How to control it:
Pre-emergent: Standard crabgrass pre-emergents (prodiamine, dithiopyr) can suppress dallisgrass seed germination when applied in early spring. They won't touch established perennial plants, but they reduce the number of new seedlings that establish in your lawn.
Post-emergent: There aren’t many good options for dallisgrass control in residential lawns. Your best bet is to physically remove it. The herbicides that are actually effective for selectively controlling dallisgrass aren’t typically labeled for use on residential lawns.
The honest truth about dallisgrass: This one takes patience. Even with the right products, plan for multiple applications over one to two seasons to get meaningful control. Mow consistently to prevent seed heads from maturing, keep your lawn thick and well-fertilized to outcompete it, and don't let it get ahead of you. Physically removing it will help you get ahead of this difficult-to-control weed.
3. Yellow Nutsedge (Cyperus esculentus)
It's not actually grass — but it fools just about everyone.
Nutsedge, often called nutgrass, is technically a sedge, not a grass, which matters a lot when it comes to choosing a herbicide. It's one of the most common weeds in southern lawns during summer, and it has a frustrating habit of growing faster than the surrounding turf after every mowing, creating those bright, unmistakable light-green streaks across an otherwise uniform lawn.
How to identify it: The easiest way to identify nutsedge is to pinch the stem. Grass stems are round. Nutsedge stems are triangular — you can actually feel the edges with your fingers. The leaves are glossy, bright yellow-green, and stiffer than typical grass blades. They grow in sets of three at the base of the plant. When mature, nutsedge sends up a distinctive seed head above the turf. You'll typically see the most growth in areas where the soil stays wet or drains poorly.
Why it keeps coming back: Nutsedge spreads by underground tubers (little nut-like structures in the soil — hence the name). Each plant can produce hundreds of new tubers per season, and those tubers can survive in the soil for years. If you pull nutsedge by hand, you almost certainly leave tubers behind, which promptly sprout new plants. For the same reason, most standard grass herbicides have absolutely no effect on it.
How to control it:
The right product matters: Because nutsedge is a sedge, not a grass, you need a sedge-specific herbicide. SedgeHammer (halosulfuron-methyl) is one of the most widely used products for nutsedge control in both warm- and cool-season turf. It's systemic, meaning it moves through the plant and down into the root system to attack the tubers. Allow two to three weeks to see full effect. A second application, six to ten weeks later, is often necessary for heavily infested areas.
Certainty herbicide is another strong option — particularly effective on warm-season turf and valued for its broad-spectrum control of sedge and Poa annua, as well as nutsedge. Add a non-ionic surfactant.
Timing matters: Apply when nutsedge is actively growing and has three to eight leaves. Don't mow two to three days before or after application.
Fix the underlying issue: Nutsedge thrives where soil stays wet. If you have persistent nutsedge, look honestly at your irrigation habits and drainage. Improving drainage and dialing back your watering frequency will make chemical control far more effective.
4. Goosegrass (Eleusine indica)
The weed that loves compacted soil — and looks just like crabgrass.
Goosegrass is frequently confused with crabgrass, and they do share some similarities. But goosegrass has its own growth habits and control quirks, and treating it like crabgrass can leave you scratching your head when results disappoint.
How to identify it: Like crabgrass, goosegrass grows in a flat, spreading pattern with stems radiating outward. The difference is in the center: goosegrass stems are distinctly flattened, and the base of the plant has a silver or whitish color — almost metallic-looking — rather than the purplish base you'd see on crabgrass. The seed heads also differ: goosegrass produces spiky, finger-like seed heads that resemble a bird's foot. You'll most often find it in areas of compacted soil or high foot traffic — driveways, lawn edges, pathways.
Why it shows up: Goosegrass is a warm-season annual like crabgrass, but it germinates a bit later — soil temperatures need to reach around 60°F before it starts sprouting. That means your early spring pre-emergent application may need a follow-up to stay ahead of it. It's particularly aggressive in compacted soils where other grasses struggle to thrive, which gives it plenty of space to establish.
How to control it:
Pre-emergent: Prodiamine and dithiopyr both provide good pre-emergent control of goosegrass when applied before soil temperatures rise above 60°F. Because goosegrass germinates later than crabgrass, a split application strategy — with the second application about six to eight weeks after the first — is valuable for keeping it out.
Post-emergent: Drive XLR8 (quinclorac) works well on goosegrass in warm-season turf. Treat it young — goosegrass that has already developed side branches is significantly harder to control.
Cultural fix: Aeration is a great long-term strategy against goosegrass. Since it loves compacted soil, loosening the soil profile and encouraging healthy turf growth takes away its competitive advantage.
5. Signalgrass (Urochloa spp.)
The crabgrass lookalike with a flag on its seed head.
Two main types of signalgrass cause problems in southern lawns: broadleaf signalgrass (Urochloa platyphylla), which is a summer annual found throughout the South, and tropical signalgrass (Urochloa subquadripara), a perennial that is particularly aggressive in Florida and the Gulf Coast states.
How to identify it: Signalgrass closely resembles large crabgrass, which makes it easy to misidentify — and misidentifying it means applying the wrong treatment. Both types have wide, flat leaf blades, but signalgrass leaves are hairless (crabgrass blades are typically hairy) and tend to be smoother. The seed head is the real identifier: the branches grow at right angles from the stem, resembling a signal flag — hence the name. Broadleaf signalgrass appears from May through October; tropical signalgrass is a warm-season perennial that comes back from stolons and seeds each year in frost-free areas.
Why it shows up: Signalgrass thrives in disturbed areas, thin turf, and anywhere there's been soil disturbance or establishment activity. Tropical signalgrass spreads by both stolons (surface runners) and seeds. It has become a significant problem in Florida specifically, where MSMA restrictions have removed one of the previously most effective tools against it.
How to control it:
Pre-emergent: Prodiamine (Resolute 65 WDG) applied in early spring helps suppress broadleaf signalgrass seed germination before it gets started.
Post-emergent: Celsius WG is labeled for signalgrass control in warm-season turf — St. Augustine, Bermuda, Zoysia, and Centipede — and is one of the better options available to residential homeowners. For broadleaf signalgrass, Drive XLR8 (quinclorac) is also effective. Tropical signalgrass is considerably harder to control, and honest expectations matter here: multiple applications over the season are required, and fall treatments tend to give the best results.
6. Carpetgrass (Axonopus affinis)
The creeping perennial that forms a thick, uninvited mat.
Carpetgrass is a warm-season perennial that spreads aggressively via stolons (surface runners), forming a dense, carpet-like mat across areas of your lawn. While it's sometimes used intentionally as a low-maintenance turf in parts of the Deep South, in a Bermudagrass or Zoysia lawn, it's an unwanted invader — especially because it looks noticeably different in texture, color, and growth pattern from the surrounding desirable grass.
How to identify it: Carpetgrass has wide, flat leaf blades with rounded tips and a coarse texture. Its most distinctive feature is the tall, slender seed stalks that shoot up in summer and fall — they're hard to miss rising above a mowed lawn. The plant tends to be paler green than most warm-season turfgrasses. It thrives in wet, poorly drained soils and low-fertility areas, which is why you'll often see it in spots where the rest of the lawn is struggling.
Why it shows up: Carpetgrass loves moisture and low-fertility conditions. If part of your lawn isn't getting adequate nutrition or is staying too wet, carpetgrass will find it. It's particularly common in the southeastern coastal states, across Louisiana, and into East Texas.
How to control it:
Post-emergent: Celsius WG is recommended for controlling carpetgrass in warm-season turf. Applications are most effective when the plant is young and actively growing, before seed production begins. A second application two to four weeks after the first, is often needed for complete control.
Cultural prevention: Improving drainage and keeping your lawn on a solid fertilization program goes a long way toward making your turf more competitive and giving carpetgrass less room to move in.
7. Doveweed (Murdannia nudiflora)
The sneaky summer annual that hides in plain sight.
Doveweed deserves its own category as one of the most underestimated weed problems in southern lawns. It's a summer annual, but unlike crabgrass, its seeds germinate later in the season — often after your spring pre-emergent has worn off — which means homeowners who ran a solid weed prevention program in spring can still end up with a doveweed problem in July or August.
How to identify it: Doveweed is easily mistaken for St. Augustinegrass or Centipedegrass because of its similar wide, glossy leaf blades. Look closely, and you'll see a few differences: the leaves are a bright, almost jewel-like green and have parallel veins and a waxy sheen. When doveweed flowers, it produces small blossoms with three distinctive purple petals — those little flowers are an unmistakable giveaway. It grows low to the ground and spreads through surface runners (stolons) that can root wherever they touch moist soil.
Why it shows up: Doveweed is a wet-soil indicator. It loves overwatered or poorly drained areas and tends to cluster around irrigation heads. If you see doveweed repeatedly in the same spots, your irrigation is almost certainly running too frequently or creating wet pockets where it shouldn't.
How to control it:
Pre-emergent: Standard spring pre-emergents typically aren't effective against doveweed because its germination window starts later, when soil temperatures reach 60 to 70°F in late spring. Specticle® FLO (indaziflam) applied in late spring specifically for doveweed prevention is one of the more effective approaches. A second application to extend the residual window helps catch the late germinators.
Post-emergent: Celsius WG is one of the best available post-emergent options for doveweed in warm-season turf. It provides good control on Bermuda, Zoysia, Centipede, and St. Augustine. A surfactant will help the herbicide penetrate doveweed's waxy leaf surface — although on St. Augustine, use extra caution with surfactant rates and check label guidance. Multiple applications are usually required.
The fix that matters most: Reduce your irrigation frequency. Deep, infrequent watering keeps soil from staying perpetually wet, which is the condition doveweed is counting on.
8. Torpedograss (Panicum repens)
The invasive perennial with underground runners that go almost everywhere.
Torpedograss earns the title of most difficult weed on this list, and it's not particularly close. It was introduced to the Gulf Coast in the late 1800s as a potential forage grass, escaped cultivation almost immediately, and is now considered a noxious weed in Alabama, Texas, and Hawaii. It's listed as a Category 1 invasive species in Florida. The name comes from the sharp, pointed tips of its underground rhizomes — they'll push through weed barrier fabric, grow under concrete, and emerge from places you'd never expect.
How to identify it: Torpedograss has flat, stiff leaf blades with a prominent midrib (center vein), giving them a slightly folded appearance. The leaves are silver-green, and the tips come to a sharp point. The above-ground stolons (surface runners) are jointed and may have fine hairs near the collar (where the leaf meets the stem). The underground rhizomes are the real identifier — white, sharply pointed, and capable of extending well over a foot below the surface. When torpedograss isn't mowed, it can reach 3 feet tall and produce small, flat, white seed heads.
Why it's so difficult: Torpedograss spreads through both above-ground stolons and an aggressive deep rhizome network. That underground system is what makes it nearly impossible to eradicate — killing the top growth forces the plant to send up new shoots from rhizomes that weren't reached. In St. Augustinegrass and Centipede lawns, this problem is compounded by the lack of selective herbicides that can remove torpedograss without also harming those grass types.
How to control it:
In Bermudagrass and Zoysia: Drive XLR8 (quinclorac) applied multiple times throughout the season is one of the more effective selective options for torpedograss in these turf types. Fusilade II (fluazifop) also has label activity on torpedograss and can be used in Zoysiagrass and fescue. Expect that control will be suppression rather than complete eradication, and plan for multiple applications over more than one season.
In St. Augustine and Centipede: This is where the honest conversation has to happen. There are currently no selective post-emergent herbicides that will control torpedograss safely in St. Augustine or Centipede. The most realistic options are carefully applied glyphosate spot treatments to kill the torpedograss (and the surrounding turf), followed by resodding or plugging those areas. Homeowners who deal with severe torpedograss in St. Augustine should seriously consider converting to Bermudagrass or Zoysia — those grasses offer far more effective chemical control options.
Prevention: Clean your mower after use in infested areas. Don't bring in untested soil or mulch. Never till areas with torpedograss — it just distributes rhizome fragments across a wider area.
Quick Identification Guide: Southern Grassy Weeds at a Glance
| Weed | Type | Key Identifier | Annual/Perennial | Go-To Product(s) |
|---|---|---|---|---|
| Crabgrass | Grassy weed | Purple stem base; finger-like seed heads at stem tips | Annual | Resolve Prodiamine (pre); Drive XLR8 (post) |
| Dallisgrass | Grassy weed | Dark-spotted seed heads on tall stems; circular clumps | Perennial | None labeled for use on residential lawns. |
| Yellow Nutsedge | Sedge | Triangular stem; glossy yellow-green; grows fast after mowing | Perennial | SedgeHammer®, Certainty |
| Goosegrass | Grassy weed | Silver/white center base; bird's foot seed head | Annual | Resolve Prodiamine (pre); Drive XLR8 (post) |
| Signalgrass | Grassy weed | Hairless, wide leaves; branches at right angles (flag shape) | Annual/Perennial | Celsius WG; Drive XLR8; Resolve Prodiamine (pre) |
| Carpetgrass | Grassy weed | Pale green; tall slender seed stalks; rounded leaf tips | Perennial | Celsius WG |
| Doveweed | Grass-like broadleaf | Waxy leaves; tiny purple flowers; clusters near irrigation heads | Annual | Celsius WG (post); Specticle® FLO (pre) |
| Torpedograss | Grassy weed | Pointed white underground rhizomes; silver-green stiff blades | Perennial | Fusilade II or Drive XLR8 (Bermuda/Zoysia); glyphosate (St. Aug/Centipede) |
Related: The Very Worst Lawn Weeds (And How to Get Rid of Them)
The Products That Work on These Weeds
Here's the honest truth: the right herbicide matched to the right weed and the right turf type makes the difference between results and frustration. Using a product that isn't labeled for your grass type, or applying it to the wrong weed, will cost you time and money. Here's a breakdown of the Golf Course Lawn products that tackle these weeds, and where each one fits.
Celsius WG Broadleaf & Grassy Weed Control
Celsius WG is probably the most versatile summer weed control product available for warm-season lawns. It controls more than 150 broadleaf and grassy weed species. It can be used safely on St. Augustine, Bermudagrass, Centipede, and Zoysia — even during the summer heat when many other products have temperature restrictions.
It should not be used on Bahiagrass or cool-season grasses like Fescue.
Drive XLR8 Herbicide — Crabgrass Control
Drive XLR8 (quinclorac) is the benchmark post-emergent for crabgrass. Still, it pulls double duty on several other grassy weeds, including goosegrass, signalgrass, and torpedograss in Bermudagrass and Zoysia lawns. It works best on plants that haven't yet reached the four-tiller stage, so timing matters. For optimal results, add a methylated seed oil (MSO) adjuvant per label directions.
Sedgehammer® Herbicide — Nutsedge Killer
Sedgehammer® is the trusted standard for nutsedge control. The active ingredient, halosulfuron-methyl, is systemic — meaning it travels down into the plant and kills the underground tubers that would otherwise keep regenerating. It works on both yellow and purple nutsedge and is safe for a wide range of warm- and cool-season turfgrasses.
Results come slowly (allow two to three weeks for visible effect) but thoroughly. A second application, six to ten weeks after the first, is often needed for heavily infested areas.
Certainty Turf Herbicide
Certainty is a powerful sedge and Poa annua herbicide for warm-season grasses. In addition to controlling nutsedge, it also controls several other tough-to-kill weeds. It is one of the few products with real efficacy against Poa annua (annual bluegrass) in warm-season lawns. It's safe for Bermuda, St. Augustine, and Zoysia and covers up to 72,000 square feet per 1.25 oz bottle.
If you're dealing with nutsedge alongside other persistent sedge problems or Poa annua pressure, Certainty is a strong all-round choice.
Celsius + Certainty Herbicide Kit
If your lawn is dealing with a mix of grassy weeds, broadleaf weeds, and nutsedge at the same time, which is common, this kit is a smart starting point. It pairs Celsius WG's broad-spectrum warm-season weed control with Certainty's targeted sedge and Poa annua performance, plus a surfactant and spray dye to make application straightforward. It's the combination approach that experienced lawn care enthusiasts use when weeds in southern lawns get complicated.
Fusilade II Herbicide — Grassy Weed Control
Fusilade II (fluazifop-p-butyl) is a selective post-emergent grassy weed killer safe for Zoysiagrass, tall Fescue, and fine Fescue lawns. It's systemic — it moves from the leaves into the roots and rhizomes — and provides control of over 45 grassy weed species. It's particularly useful for removing Bermudagrass from Zoysia or Fescue lawns and suppressing torpedograss and dallisgrass in those same grass types.
It can also be combined with Recognition herbicide for use in St. Augustinegrass, but it cannot be used alone on St. Augustine — check the label carefully. It will damage or kill most other warm-season grasses if applied at full rates.
Resolute Prodiamine 65 WDG — Pre-Emergent
Resolute Prodiamine 65 WDG is a professional-grade pre-emergent that forms a chemical barrier in the soil to stop weed seeds from germinating. It's the backbone of any pre-emergent program for southern lawns. It provides season-long residual activity against crabgrass, goosegrass, signalgrass, and a wide range of summer annual grassy and broadleaf weeds.
The key is timing — apply before soil temperatures at 2 inches reach 50 to 55°F for crabgrass, or before they hit 60°F for goosegrass and signalgrass. A split-application approach (first app in early spring, follow-up six to eight weeks later) gives you the best, longest-lasting coverage.
Specticle® FLO Pre-Emergent Herbicide
Specticle® FLO (indaziflam) is one of the most effective pre-emergent options available, particularly valuable for extended-residual weed prevention and for controlling weeds that evade standard pre-emergents. It's especially recommended for doveweed prevention in warm-season turf — its longer soil residual covers doveweed's late germination window better than many other pre-emergents. It's safe for Bermudagrass, St. Augustine, Centipede, and Zoysia.
Related: Japanese Stiltgrass: The New Invasive Threat to Lawns
FAQs: Grassy Weeds in Southern Lawns
How do I tell crabgrass and dallisgrass apart?
They're easy to confuse, but the seed heads give them away. Crabgrass seed heads grow in a fine-textured cluster at the very tip of the stem. Dallisgrass seed heads grow along the stem, with a coarser texture and distinctive dark spots. Dallisgrass also forms more pronounced circular clumps and returns every year; crabgrass dies off in the fall and germinates anew each spring.
Why does nutsedge grow so much faster than my grass after I mow?
Because nutsedge is a sedge — a different plant family entirely — it grows at a different rate than your turfgrass and isn't slowed down by mowing the way grass is. That rapid regrowth after mowing is one of the most reliable ways to spot it. The other is to look for that characteristic bright yellow-green color standing out above the surrounding turf.
Can I use a standard grass killer on nutsedge?
No, and this is a really common mistake. Most herbicides that kill crabgrass and other grassy weeds do not affect nutsedge because it's technically a sedge, not a grass. You need a sedge-specific product, such as SedgeHammer® (halosulfuron) or Certainty. Using the wrong product just wastes your time and money.
My pre-emergent didn't stop the crabgrass — what happened?
A few possibilities. The most common reasons: it was applied too late (after soil temperatures had already reached 55°F), it wasn't watered in adequately after application, or the residual wore off before the main crabgrass germination window closed. A split application strategy — one early spring application of Resolute Prodiamine followed by a second six to eight weeks later — gives you much more consistent season-long coverage.
Is dallisgrass safe to treat myself, or do I need a professional?
Heavy dallisgrass infestations are genuinely challenging. If you've got large clumps throughout the lawn, it may be worth consulting a lawn care professional who has access to commercial-grade products and can map out a multi-season control plan. There's no shame in getting help with a stubborn problem. The best way to combat dallisgrass in a residential lawn is physically removing it.
Is doveweed the same thing as crabgrass?
No — and this distinction matters for treatment. Doveweed is actually a broadleaf plant that looks grass-like, rather than a true grassy weed. It germinates much later in the season than crabgrass (late spring to early summer), which is why standard spring pre-emergents often miss it. Specticle® FLO is the pre-emergent best suited to its later germination window, and Celsius WG is a post-emergent. The two weeds look very different up close — doveweed has wide, glossy leaves and tiny purple flowers; crabgrass does not flower like that.
Can I get rid of torpedograss in my St. Augustine lawn?
This is one of the toughest conversations in southern lawn care. The honest answer is: not selectively. There are no post-emergent herbicides currently labeled to control torpedograss without also damaging St. Augustine. Your real options are carefully applied glyphosate to kill infested patches (and then resodding), or, for severe infestations, considering a switch to Bermudagrass or Zoysia, which opens up options like Drive XLR8 and Fusilade II for torpedograss control.
What's the difference between carpetgrass and my desirable lawn grass?
Carpetgrass has wider, more rounded leaf tips than most warm-season grasses and sends up unmistakable tall, slender seed stalks above the turf line in summer. Its color is also paler. It thrives in wet, low-fertility spots — so if you see it clustered in the same areas repeatedly, improving drainage and your fertilization program will help your desirable grass outcompete it over time. Celsius WG handles it well as a post-emergent.
Will a healthy lawn really help prevent these weeds?
Absolutely — and this isn't just feel-good advice. Grassy weeds need space and light to establish. A thick, dense lawn that's properly fertilized, mowed at the right height, and well-watered leaves very little room for weeds to get started. Cultural practices won't completely replace herbicide programs, but they make a measurable difference over time.
When should I apply a pre-emergent for crabgrass in the South?
In the Deep South (Florida, southern Texas, coastal areas), you'll want your first application down by late January to mid-February. Through most of the Southeast and mid-South, target late February to early March. The goal is to get it in the ground before soil temperatures consistently hit 55°F. A second application of Resolute Prodiamine, six to eight weeks later, significantly extends your protection window.
Does signalgrass need a different herbicide than crabgrass?
Not always, but the distinction matters in some cases. Celsius WG controls both and is your best broad-spectrum option in warm-season turf. Drive XLR8 (quinclorac) controls crabgrass and broadleaf signalgrass well. Tropical signalgrass — the persistent perennial form found mainly in Florida — is considerably harder to control and usually requires a specific multi-application fall treatment program.
Related: How to Kill Virginia Buttonweed
Your Lawn Called. It Wants Its Grass Back.
Summer weed pressure in southern lawns is real, and the grassy weeds that blend right into your turf are the sneakiest of the bunch. Whether it's crabgrass germinating in a thin spot, nutsedge shooting up after every mow, doveweed creeping around your irrigation heads, or torpedograss running its underground marathon — each weed has its own characteristics, timing, and control requirements.
The sooner you identify what you're dealing with, the easier it is to manage. A solid pre-emergent program in spring takes care of the annuals. The right post-emergent herbicide — matched carefully to both the weed and your grass type — handles what breaks through. And consistent, solid lawn care habits make your turf genuinely resilient against weed pressure over the long run.
You've got this. And we've got the products to back you up.
If those grassy impostors have been giving you grief all summer, you're not stuck guessing. At Golf Course Lawn, we carry professional-grade weed killers, fertilizers, and soil health products designed to help you get on top of the weeds covered in this guide — and keep them from coming back. And if you want to see these products in action before you buy, check out our videos on the Golf Course Lawn YouTube channel.
Ron Henry
Ron Henry is the founder of Golf Course Lawn, which is dedicated to helping homeowners achieve golf course-quality lawns. He holds a certificate in Sports Turfgrass Management from the University of Georgia. With expert knowledge in turf care, fertilization, and weed control, he shares practical tips and product recommendations to create lush, healthy lawns.