What Kills Crab Grass in Lawns? A Complete Guide

Crabgrass is one of the most problematic weeds that can infest lawns. This annual grassy weed thrives in the summer, spreading quickly to form unsightly patches in turfgrass. Controlling crabgrass takes effort, but it can be done through various methods. In this comprehensive guide, we’ll explore what kills crabgrass in lawns, from natural remedies to chemical herbicides.

What is Crabgrass?

Crabgrass (Digitaria spp) is a fast-growing annual weed that propagates through seeds The weed prefers full sun and disturbed soils. It germinates in spring when soil temperatures reach 55-60°F. Crabgrass has coarse, wide blades and grows close to the ground in circular clumps up to 6 inches wide. The stems radiate outwards resembling crab legs, hence the name. Left unchecked, each plant can produce up to 150,000 seeds, creating problems for years to come.

Crabgrass competes with turfgrass for water, nutrients and sunlight. It can take over thinning lawns, causing bare patches. Crabgrass also decreases the aesthetic value of lawns with its unsightly, discolored appearance. Controlling crabgrass as soon as it appears is crucial in maintaining a healthy, weed-free lawn.

Why Kill Crabgrass?

There are several compelling reasons to control and eliminate crabgrass in lawns:

• Crabgrass is unattractive, damaging curb appeal.
• It crowds out and weakens desirable grass.
• Each plant produces thousands of seeds that germinate the following years.
• Crabgrass harbors other lawn pests like chinch bugs.
• The weed invades thin, undernourished areas of lawn.
• It hog nutrients and moisture meant for turfgrass.
• Crabgrass can take over an entire lawn if left unchecked.

When to Kill Crabgrass

Spring: Apply pre-emergent crabgrass preventers when forsythia blooms fade. This stops seeds from sprouting.

Summer Use post-emergent herbicides on young crabgrass for best results Mature plants are harder to kill

Fall: Avoid treating crabgrass once it turns brown and dies back. Focus on improving lawn health to prevent future growth.

Timing is critical when using any crabgrass control method. Treat it early before it can set seed.

Natural Ways to Kill Crabgrass

For those wishing to avoid chemicals, here are some non-toxic methods to kill crabgrass naturally:

1. Manual Removal

Hand-pulling crabgrass is effective for young plants. Use a dandelion puller or crabgrass removal tool to extract roots. Discard plants immediately to prevent reseeding. This labor-intensive method works best on small infestations.

2. Boiling Water

Pour boiling water directly on crabgrass to scald and kill it. Avoid harming desirable grass by using a sprinkling can to target individual weeds. Boiling water is non-selective and will damage any plants contacted.

3. Vinegar

Spray full-strength, horticultural vinegar onto crabgrass leaves to burn and desiccate the weed. Use caution to only spray weeds, as vinegar can harm turfgrass when overapplied. It may take several treatments to fully kill crabgrass with this method.

4. Corn Gluten Meal

This organic pre-emergent prevents crabgrass seeds from germinating when applied early spring. It does not kill existing crabgrass but can help control future growth. Strict spring timing and repeat applications are crucial for success.

5. Flame Weeding

Using a propane torch to briefly burn crabgrass will heat-shock and dehydrate the weed. This method requires precision and works best on young crabgrass. Avoid excess heat that can damage lawn grass. Flame weeding works instantly with no harmful chemical residue.

Chemical Crabgrass Killers

For large infestations, herbicide application is the most effective approach to eradicate crabgrass. Always carefully follow label directions when using any chemical control:

Pre-Emergent Herbicides

Applied in early spring before germination, these preventive crabgrass killers stop seeds from developing into plants. Some options include prodiamine, pendimethalin and dithiopyr.

Post-Emergent Herbicides

These selectively target actively growing crabgrass to kill emerged weeds. Quinclorac, fenoxaprop, mesotrione and sulfentrazone are common active ingredients in post-emergent crabgrass killers.

Non-Selective Herbicides

Products containing glyphosate will kill all plant material, including lawn grasses. Use them cautiously as spot treatments only on crabgrass. Avoid contact with desired vegetation.

Natural Herbicides

Some crabgrass killers derive from natural ingredients like citric acid, eugenol or iron HEDTA. These provide non-toxic weed control when applied correctly per label guidelines.

7 Tips for Controlling Crabgrass

Follow these lawn care practices to prevent crabgrass infestations:

• Maintain dense, healthy turfgrass that crowds out weeds.
• Mow high (3-4 inches) to shade the soil surface.
• Water deeply and infrequently to encourage deep root growth.
• Use pre-emergent herbicides for early season control.
• Apply post-emergent herbicides on young crabgrass plants.
• Pull isolated crabgrass plants by hand before they seed.
• Overseed bare spots in the lawn to prevent crabgrass encroachment.

Vigilance and quick action are key to keeping crabgrass from taking over your lawn. Implementing multiple control methods provides the best chance of success in eradicating this stubborn annual weed for good.

No, vinegar is generally not a permanent solution for killing crabgrass. While it can damage or kill the visible parts of the plant, it often doesn’t reach the roots, allowing the crabgrass to regrow.