As any homeowner with a lawn knows, crabgrass can be one of the most frustrating weeds to deal with. This annual grassy weed thrives in summer, spreading rapidly to form unsightly patches that disrupt the uniformity and health of turfgrass.
Getting rid of crabgrass takes some effort, but it can be done. This comprehensive guide will walk you through effective crabgrass control strategies to kill existing plants and prevent future growth.
What is Crabgrass?
Crabgrass (Digitaria spp) is a fast-growing annual weed that propagates through seeds, It germinates in spring when soil temperatures reach 55-60°F and dies off with the first frost
Some key traits of crabgrass include:
- Coarse, light green leaf blades with blunt ends that grow close to the ground
- Sprawling growth habit, spreading via aboveground stolons to form patches
- Seed heads borne on thin stalks rising above foliage
- Shallow root system concentrated in the top few inches of soil
Unlike perennial grassy weeds, crabgrass dies completely in late fall or early winter after setting seed. But each plant can produce up to 150,000 seeds, ensuring recurring generations.
Its ability to thrive in poor, compacted soils makes crabgrass a common problem in thin, neglected lawns. The weed competes aggressively with desirable turfgrass for light, water and nutrients.
Manual Removal of Crabgrass
Manually digging out crabgrass with a hand trowel or weeding tool is effective for young plants or sparse infestations. Take care to remove all roots and stolons to prevent regrowth.
For larger, mature plants, manual removal risks pulling up chunks of lawn as the weeds are closely intertwined with surrounding turf. Attempting to yank out extensive crabgrass growth is labor-intensive and can leave bare patches for more weeds to colonize.
Dispose of uprooted crabgrass plants immediately before they can release seeds. Monitor the area and re-dig any regrowth.
Using Post-Emergent Herbicides
Post-emergent crabgrass killers containing active ingredients like quinclorac, fenoxaprop and MSMA selectively target actively growing crabgrass while leaving desirable lawn grasses unharmed.
Timing applications is crucial – crabgrass killers work best on young, actively growing plants in early summer. Established plants can be more difficult to control.
Spot treatment of individual weeds or patches is ideal. Thoroughly wet all foliage. It may take 1-2 weeks for herbicides to fully kill crabgrass. Repeat applications are sometimes needed.
Post-emergent herbicides provide quick knockout of existing crabgrass. But pre-emergents are still required to prevent future growth from the seed bank.
Stopping Crabgrass Before It Emerges
Since each crabgrass plant produces thousands of seeds, pre-emergent control is key for lasting results. Crabgrass preventers create a chemical barrier that stops seeds from germinating and seedlings from establishing.
Applying pre-emergent herbicides like prodiamine, pendimethalin or dithiopyr in spring before soil temperatures reach 55-60°F provides season-long control by preventing the first flush of crabgrass.
Timing is critical. For best results, apply pre-emergents when forsythia shrubs are in full bloom. This coincides with optimal crabgrass germination temperatures.
Watering in preventers activates the chemical barrier. Reapply every 2-3 months as directed to maintain control through summer. They won’t affect established plants, so combine with post-emergents to kill existing weeds.
Improving Lawn Health and Density
The best defense against crabgrass is a healthy, lush lawn. Turfgrass that is thick and dense leaves little room for weeds to invade.
Follow proper mowing, watering, fertilization and aeration practices to grow a vigorous lawn that out-competes crabgrass. Overseed bare or thinning areas in fall.
Mowing high (3-4 inches) promotes deeper roots and increased density. Leave clippings for free fertilizer. Ensure lawns get 1-1.5 inches of water per week, including rainfall.
Fertilize at least twice yearly. Dethatch or aerate to improve soil composition, drainage and reduce compaction.
Top Crabgrass Control Tips
Here are some key tips for getting rid of crabgrass for good:
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Hand pull small infestations. Be sure to get all roots and runners.
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For mature plants, use selective post-emergent herbicides labeled for crabgrass.
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Apply pre-emergent crabgrass preventers in early spring before soil temperatures reach 55-60°F.
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Reapply preventers every 2-3 months through summer to keep seedlings from sprouting.
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Improve lawn density through proper mowing, fertilizing, aerating and overseeding to prevent weed invasion.
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Conduct early intervention by controlling young crabgrass plants as soon as you see them sprout.
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Do not mow, dethatch or aerate 2-4 weeks before or after applying pre-emergents.
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Irrigate preventers immediately after application to activate the chemical barrier.
Common Crabgrass Control Questions
Here are answers to some frequently asked questions about killing crabgrass:
When is the best time to apply pre-emergent herbicides?
Early spring before soil temperatures reach 55-60°F. This coincides with crabgrass germination.
How often should I apply crabgrass preventers?
Reapply every 2-3 months through summer to maintain the chemical barrier as directed.
Can I use vinegar or boiling water to kill crabgrass?
No, homemade remedies like these are ineffective against mature crabgrass. Use selective herbicides.
Is crabgrass preventer safe for pets and kids?
Most pre-emergents have low toxicity when dry. Follow product instructions to minimize exposure risk.
Should I dig up crabgrass or spray it with herbicide?
Digging is suitable for young plants only. Mature crabgrass is best controlled with selective post-emergent herbicides.
What’s the difference between pre- and post-emergent crabgrass killers?
Pre-emergents prevent seeds from sprouting. Post-emergents kill established actively growing plants. Use both.
Controlling crabgrass takes diligence, but combining pre- and post-emergent herbicides with good cultural practices for optimal lawn health provides effective, lasting control.
The key steps are early spring pre-emergent application, treating young plants with post-emergents promptly, and improving turf density to withstand invasion.
With a comprehensive IPM approach, you can knock out existing crabgrass and keep new generations from establishing themselves in your lawn. Just remember persistence and timing are vital to gain the upper hand against this stubborn annual weed.
How to Get Rid of Crabgrass (4 Easy Steps)
How do you kill crabgrass?
There are other methods you can try to kill crabgrass that won’t impact the surrounding lawn, such as mulching the crabgrass, boiling water, and smothering the crabgrass with paver blocks. Crabgrass is an opportunistic grass that can invade a manicured lawn or perennial flower bed.
How do you remove crabgrass from a lawn?
While this method works fine for small, immature sections of crabgrass, which you should pull up as soon as you spot, you should take care if your crabgrass is well-established. If you attempt to remove a large clump of crabgrass with a manual tool, you could pull up a chunk of your lawn with it as well, thanks to the deep root system.
How do I prevent crabgrass weeds?
There are a few ways to prevent crabgrass. In addition to applying a crabgrass weed preventer to your lawn, you should also fertilize your lawn regularly to keep it healthy, keep your lawn tall, make sure your lawn gets enough water, and dethatch and aerate.
Does vinegar kill crabgrass?
Yes, vinegar can kill crabgrass. You’ll want to ensure you’re using gardening vinegar, however, and not household vinegar. Fill a spray bottle, spray the area, and repeat until the crabgrass is killed off. How can you kill crabgrass but not the surrounding grass?