Crabgrass: identify it, treat it, keep it out
Crabgrass is the most common summer annual weed in American lawns. It germinates when soil hits the mid-50s in spring, sprawls into wide, crab-legged clumps through summer, then dies at frost and leaves bare spots that reseed next year. Prevention timing beats curative spraying almost every time.
How to identify crabgrass
- Wide, flat blades that are noticeably lighter green than the surrounding lawn
- Stems radiate from a central point like crab legs, hugging the ground
- Clumps show up first along driveways, sidewalks, and thin sunny spots where soil warms fastest
- Finger-like seed heads splay from the stem tips in late summer
- Pulls up easily as a single rosette with shallow roots
Don't confuse it: Often confused with tall fescue clumps (darker green, upright, deep-rooted) and dallisgrass (perennial, returns from the same spot each year).
Not sure this is your weed? Snap a photo and our AI will identify the problem with treatments matched to your grass type.
When to treat
Prevention (pre-emergent)
Apply before germination, when soil reaches about 55°F.
Window: Late winter to early spring
Typical dates: Before soil reaches 55°F for 3 consecutive days
Treatment (post-emergent)
Best time: Early summer when young
Target stage: Before tillering (4-6 leaf stage)
Conditions: Apply when weeds are dry · No rain for 24 hours · Temps below 85°F
Germination starts around 55°F soil temperature (optimal 65°F). Track your ZIP's live soil temperature or get an exact plan from the herbicide timing calculator.
Control plan
- 1Apply pre-emergent before soil reaches 55°F
- 2Maintain thick, healthy grass to prevent establishment
- 3Avoid overwatering in summer
- 4Consider overseeding in fall to improve density
Good to know
- • Most effective as pre-emergent
- • Can be controlled post-emergent when young
- • Produces thousands of seeds per plant
- • Thrives in compacted soil
Products that work on crabgrass
These picks are not filtered to your lawn. Some herbicides damage certain grasses (atrazine is for warm-season lawns; Trimec harms St. Augustine). Verify your grass type on the product label before applying, or use the herbicide timing calculator for grass-filtered recommendations. As an Amazon Associate we earn from qualifying purchases.
curative
BASF Drive XLR8 Crabgrass Killer (Quinclorac)
Water-based quinclorac concentrate for post-emergent control of crabgrass and listed broadleaf weeds when they have already broken through.
Quinclorac is the post-emergent crabgrass pick when it is safe for the grass.
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preventive
Barricade 4FL Herbicide Concentrate (4 Fl Oz)
Prodiamine pre-emergent concentrate for established lawns when the guide specifically calls for long-residual crabgrass prevention. The 4 oz bottle treats roughly half an acre at the standard label rate.
Prodiamine prevents the next crabgrass wave before it germinates.
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preventive
Dimension 2EW
Dithiopyr pre-emergent that also provides early post-emergent activity on young crabgrass escapes.
Dithiopyr also helps on very young crabgrass escapes.
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Where it's most common
Frequently asked questions
When should I apply crabgrass preventer?
Apply pre-emergent when soil temperature reaches about 55°F for several consecutive days, which is usually when forsythia blooms. In most of the country that is early to mid spring. Our soil temperature tool tracks your ZIP so you can time it precisely.
Can I kill crabgrass in summer?
Yes, with a post-emergent herbicide containing quinclorac while plants are young. Mature August crabgrass is much harder to kill, and it dies at first frost anyway, so late-season spraying is often not worth it. Focus on prevention next spring instead.
Why does crabgrass keep coming back every year?
One plant drops thousands of seeds that stay viable in soil for years. Skipping pre-emergent for a single season lets that seed bank germinate. Two to three consecutive years of well-timed prevention plus a thicker lawn breaks the cycle.
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