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Knowing how to get rid of crabgrass without killing grass comes down to one thing more than anything else: timing. The right product used at the wrong point in the season does almost nothing. Use it correctly, and you can clear out what’s already growing and prevent next year’s seeds from ever sprouting. This guide covers both — what to do when crabgrass is already there, and how to stop it before it starts.
What Crabgrass Is and Why It Keeps Coming Back
It tends to show up first in the stressed, thin parts of a lawn — along sidewalks, near driveways, in bare spots and compacted areas. Dense, healthy turf shades the soil and blocks the warm temperatures crabgrass seeds need to germinate. Where the turf is thin, crabgrass finds an opening.
One plant can produce up to 150,000 seeds in a single season. That’s why a small patch left untreated in July becomes a much larger problem the following spring.
Pre-Emergent vs. Post-Emergent: Two Different Problems
Before choosing a product, you need to answer one question: has the crabgrass already sprouted, or are you trying to stop it before it does?
Pre-emergent herbicides create a chemical barrier in the soil that prevents seeds from germinating. They do nothing to plants already growing. Post-emergent herbicides kill actively growing plants. They do nothing to seeds still in the soil. Most persistent crabgrass problems need both, used in the right season.
How to Get Rid of Crabgrass That’s Already Growing
If you can see crabgrass plants in your lawn right now, you need a selective post-emergent herbicide — one that targets crabgrass without harming your turf grass.
Mesotrione (Tenacity / Torocity) — Best for Cool-Season Lawns
Mesotrione is a systemic herbicide that works on both pre- and post-emergent crabgrass. It’s safe to use on Kentucky bluegrass, tall fescue, and perennial ryegrass — and it’s one of the only herbicides labeled for use at seeding time, which makes it especially useful for fall lawn renovations. According to Penn State Extension, mesotrione provides effective post-emergence control of crabgrass when applied to plants with fewer than four tillers — younger plants respond better.
Expect the treated crabgrass to turn white and bleached within a few days. That whitening is the herbicide working, and it lasts two to three weeks before the plant dies. Plan on two to three applications spaced two to three weeks apart for complete control.
Two things are required every time you spray mesotrione: a non-ionic surfactant (so the product actually sticks to the leaf surface) and ideally a spray indicator dye so you can see where you’ve already applied and avoid missed spots.
Syngenta Tenacity is the original brand. For a lower-cost option with the same active ingredient, Atticus Torocity contains the same 40% mesotrione concentration at a better price per ounce.
Apply the Syngenta Tenacity Herbicide to young crabgrass plants using ½ teaspoon per gallon of water plus surfactant, spot-spraying directly on affected areas.
Budget option: the Atticus Torocity Mesotrione uses the same chemistry at a lower cost — same application method, same rules.
Always mix with a non-ionic surfactant – without it, mesotrione won’t adhere to the leaf surface well enough to work. Adding a Lazer Blue spray indicator dye to your tank mix shows you exactly where you’ve sprayed, preventing overlaps and missed spots.
Do not apply mesotrione to bentgrass, zoysiagrass, or bermudagrass. Check your grass type on the product label before spraying.
Quinclorac — Better for Mature Crabgrass
If your crabgrass is large and established with multiple stems spreading from a central root, quinclorac is a stronger option. According to Michigan State University Extension, quinclorac provides effective control of crabgrass at almost any growth stage — including mature plants that mesotrione struggles with. It also controls some broadleaf weeds like dandelion and clover as a bonus.
One important restriction: quinclorac is not safe for St. Augustine or centipede grass lawns. If you have either of those, mesotrione is the correct choice.
Application Tips
Spray in the morning or evening — applying in midday heat above 90°F increases the risk of temporary turf discoloration, especially on perennial ryegrass. Water the lawn lightly if no rain falls within seven to ten days of application; moisture helps systemic herbicides move through the plant. Target plants with fewer than four tillers for the best results with mesotrione.
How to Prevent Crabgrass Before It Starts
Post-emergents handle what’s already growing. But the long-term fix is stopping seeds from germinating in the first place — that’s the job of a pre-emergent herbicide applied each spring.
Timing Your Pre-Emergent
Pre-emergents only work before germination. Once you can see seedlings, they won’t help those plants. Crabgrass seeds begin germinating when soil temperatures reach 55°F for four to five consecutive days at a three-inch depth. In the Midwest and Northeast, that’s typically late March through mid-April. A practical timing cue: apply when forsythia shrubs in your area finish blooming — it’s a reliable natural signal that soil temps are entering the germination zone.
Scotts Halts — Granular, Easy to Apply
Scotts Halts is the most widely available pre-emergent option for homeowners. Apply the granules with a broadcast spreader to a dry lawn, then water in. One 10-lb bag covers about 5,000 square feet. It prevents crabgrass, foxtail, barnyardgrass, and several other grassy weeds all season long from a single application.
Important: do not use on newly seeded lawns. Wait until after the fourth mowing before applying to new grass.
Apply Scotts Halts Crabgrass Preventer in early spring before soil temps hit 55°F. Use a broadcast spreader and water in after application.
Prodiamine 65 WDG — Professional-Grade Option
Prodiamine is what lawn care companies use. It provides season-long control and is more cost-effective per square foot on larger lawns. It comes as a water-dispersible granule that you mix into a spray solution — more precise measuring required, but longer-lasting results. Like all pre-emergents, it will also prevent grass seed from germinating, so don’t use it if you plan to overseed within 60 days.
For larger lawns or anyone who wants the same product the pros use, Prodiamine 65 WDG delivers reliable season-long pre-emergent control at a better cost-per-square-foot than granular bag products.
Note: if you’re planning to overseed this fall, skip the pre-emergent and use mesotrione (Tenacity/Torocity) instead — it’s the only herbicide labeled for use at seeding time.
Lawn Habits That Make Crabgrass Give Up
Herbicides handle what’s already there. A thicker, healthier lawn is what keeps crabgrass from coming back. It can’t compete with dense, established turf — it only gets a foothold where the grass is thin or stressed.
Mow higher. Oregon State University Extension recommends mowing cool-season grasses at three to four inches. Taller grass shades the soil, keeping it cooler and cutting off the direct sunlight crabgrass seeds need to germinate. OSU Extension mowing height for crabgrass prevention.
Water deeply, not frequently. Shallow daily watering produces shallow roots, which weakens turf and gives crabgrass an opening. One deep watering per week is better for grass health than light watering every day.
Fill bare spots. Every bare patch is a potential germination site for next year’s crabgrass. Overseed thin areas in fall — for cool-season grasses, fall is the ideal window. See the “how to overseed a lawn in fall” guide for the full process.
Don’t spread crabgrass seed by mowing. If crabgrass in your lawn has already set seed, mowing can distribute those seeds across the rest of the lawn. Bag and dispose of clippings from heavily infested areas to reduce next year’s seed bank.
What Won’t Work on Crabgrass
Weed-and-feed fertilizers. Most use broadleaf selective herbicides that kill dandelions and clover. Because crabgrass is a grassy weed, not a broadleaf weed, most weed-and-feed products have no effect on it at all.
Pulling by hand. It works for very small patches on moist soil, but it’s only useful before the plant has set seed. Any plant that’s already dropped seed leaves those seeds behind in the soil regardless.
Waiting until fall. Mature crabgrass dies with the first frost whether you treat it or not. But by mid-summer it has already produced seed. Treating it after seed set does nothing to reduce next year’s problem.
The Year-Over-Year Strategy
Crabgrass doesn’t get resolved in one season — but it does get smaller each year if you stick to the same cycle.
Spring: Apply pre-emergent before soil temps hit 55°F. Scotts Halts or Prodiamine are both solid choices. Skip this step only if you’re planning to overseed.
Summer: Spot-treat any crabgrass that breaks through with mesotrione or quinclorac. Add a surfactant, plan on two applications three weeks apart.
Fall: Overseed thin areas to close the bare spots crabgrass exploits. This is the highest-leverage move in the whole plan — a denser lawn next spring means fewer openings for crabgrass to germinate.
Each year you repeat this cycle, the seed bank in your soil shrinks and the infestations get smaller.
Sources & Further Reading
- Penn State Extension. “Postemergence Control of Crabgrass and Other Summer Annual Grasses in Lawns.”
- Michigan State University Extension. “Controlling Crabgrass After It Emerges.”
- Oregon State University Extension Service. “How Do I Get Rid of Crabgrass?”