How to Get Rid of Crabgrass: A Step-by-Step Guide

Crabgrass is the most common and frustrating summer weed in American lawns. It germinates in warm soil, spreads aggressively in bare and thin areas, and produces up to 150,000 seeds per plant before dying at first frost. The good news: crabgrass is entirely preventable with the right approach — and it fits into a broader lawn weed control guide covering everything from pre-emergent timing to post-emergent treatment. Here’s exactly how to eliminate it and keep it from coming back.

Understanding the Enemy: Crabgrass Biology

Crabgrass is a summer annual—it lives for one season, produces massive amounts of seed, and dies with the first frost. The seeds remain dormant in the soil over winter, then germinate the following spring when soil temperatures reach 55–60°F consistently.

There are two main species in the US:

• Smooth crabgrass (Digitaria ischaemum): Smaller, common in northern lawns
• Large/hairy crabgrass (Digitaria sanguinalis): Bigger, more common in southern lawns

Both behave identically from a control perspective. The important thing to understand is that crabgrass is an annual—if you can prevent seed germination or kill plants before they set seed, you break the cycle.

Step 1: Apply Pre-Emergent Herbicide at the Right Time

Pre-emergent herbicide is the most effective crabgrass control method. It creates a chemical barrier in the soil that kills crabgrass seeds as they germinate—before you ever see them. Understanding exactly how pre-emergent and post-emergent herbicides differ helps you pick the right product at the right time.

The timing secret: Apply when soil temperatures at 2-inch depth reach 50–55°F for 3 consecutive days. Air temperature forecasts don’t determine this—you need soil temperature.

Timing indicators:

• Northeast/Upper Midwest: Mid-April to early May (when forsythia is blooming)
• Mid-Atlantic/Pacific NW: Late March to mid-April
• Transition Zone: Mid-March to early April
• Southeast/Southwest: February to mid-March

Your spring lawn care checklist can help you time this application alongside your other early-season tasks.

Products that work:

• Prodiamine (Barricade): One of the most effective; long residual (3–5 months); comes as granular or liquid
• Pendimethalin: Granular or liquid; commonly found in Scotts Crabgrass Preventer
• Dithiopyr (Dimension): Unique property—also controls very young crabgrass seedlings in addition to pre-emergent activity
• Corn gluten meal: Organic option with limited efficacy; best used consistently over several years

Application tips:

• Apply granular pre-emergent with a broadcast spreader at the labeled rate—too little won’t work; too much can harm grass
• Water in with ¼–½ inch of irrigation within 24–48 hours to activate
• A split application (half in spring, half 6–8 weeks later) provides better season-long control
• Don’t apply before seeding: Pre-emergents kill grass seed too. Wait 60–90 days after application before seeding, or use dithiopyr which has a shorter restriction window.

Step 2: Identify and Target Escaped Crabgrass

Despite your best efforts, some crabgrass may escape pre-emergent protection—especially in areas where the barrier was disrupted by foot traffic, rain, or incomplete coverage.

What to look for: Light green to yellow-green patches (lighter than your lawn grass), with wide flat blades that radiate outward from a central crown. As summer progresses, you’ll see characteristic “crab” seed head spikes extending in 3–9 “fingers.”

Act early: Post-emergent control is most effective on young crabgrass with 2–4 leaves (tillers). Large, mature crabgrass is much harder to kill.

Step 3: Apply Post-Emergent Treatment

Once crabgrass is actively growing, you need a post-emergent herbicide. Options are more limited than for broadleaf weeds.

Quinclorac (Drive XLR8, Quali-Pro): The most effective post-emergent for crabgrass. Works best on young plants. Must be combined with a methylated seed oil (MSO) adjuvant for maximum effectiveness—many products include this, but check the label.

Fenoxaprop (Acclaim Extra): Works well, but has restrictions on some grass types. Check label for your lawn grass compatibility.

Fluazifop: Effective on young crabgrass; labeled for many situations.

Hand pulling: Effective if done early, before plants set root deeply. Pull after a rain or irrigation when soil is moist. Wear gloves—crabgrass has silica crystals that irritate skin. Discard (don’t compost) pulled plants that have any seed heads.

What doesn’t work:

• 2,4-D, dicamba, and other broadleaf herbicides: Do nothing to grassy weeds like crabgrass
• Glyphosate (Roundup): Non-selective—kills crabgrass but also kills your lawn grass. Only use for spot treatment in areas you’ll reseed.

Application timing: Apply post-emergent in the morning when temperatures are below 85°F. Hot-weather applications can cause turf burn. Don’t apply during drought stress.

Step 4: Address Mature Late-Season Crabgrass

By mid-August, crabgrass is often too large and too well-rooted for cost-effective chemical control. At this point, your strategy changes:

• Don’t try to kill it—it will die at first frost anyway
• Prevent seed drop: If you must mow over mature crabgrass, bag the clippings to prevent seed dispersal
• Mark heavily infested areas: Plan to aerate, overseed, and apply pre-emergent in those areas the following spring
• For intolerable infestations: Spot-treat with glyphosate and reseed the area (wait 3–7 days after glyphosate application for most products)

Step 5: Fill Bare Spots After Crabgrass Dies

This is the step most homeowners skip—and why crabgrass comes back every year.

When crabgrass dies at first frost, it leaves bare soil. Bare soil is exactly where crabgrass seeds germinate next spring. Fill bare spots with grass seed in late summer to early fall (the best window for cool-season grass seeding):

1. Rake out dead crabgrass
2. Loosen soil with a rake or power dethatcher
3. Apply grass seed at overseeding rates
4. Apply starter fertilizer
5. Water daily for 2–3 weeks
6. Don’t apply pre-emergent this fall if you’re seeding—wait until the following spring

Dense, established grass is your best protection against crabgrass the following year. If you prefer to avoid synthetic herbicides throughout this process, organic lawn care methods like corn gluten meal and cultural practices offer a chemical-free path to prevention.

Long-Term Crabgrass Prevention

Preventing crabgrass is far easier than eliminating it. A comprehensive approach:

Annual pre-emergent application: Apply every spring without fail. Even one missed year allows seeds to accumulate in the soil.

Maintain proper mowing height: Taller grass (3–4 inches for cool-season grass) shades the soil and prevents crabgrass seeds from receiving the light they need to germinate. This is one of the most consistently underrated crabgrass prevention strategies.

Overseed thin areas in fall: Dense grass has no room for crabgrass. Thin, sparse turf is an open invitation.

Core aerate annually: Reduces soil compaction where crabgrass thrives and improves grass density.

Avoid overwatering: Daily shallow watering keeps the surface soil moist—exactly what crabgrass seeds need to germinate. Water deeply and infrequently instead.

Reduce soil disturbance: Disturbed soil brings buried crabgrass seeds to the surface where they can germinate. Avoid unnecessary tilling or raking in spring.

Crabgrass Control Quick-Reference

Situation	Solution
Prevention	Pre-emergent in spring at soil temp 50–55°F
Young crabgrass (few tillers)	Quinclorac post-emergent
Mature crabgrass	Wait for frost; prevent seed drop
Large bare areas	Spot treat with glyphosate, reseed in fall
Recurring annual problem	Pre-emergent + fall overseeding

Crabgrass can be beaten—but it requires consistent action. One year of proper pre-emergent timing, combined with overseeding bare spots, makes a bigger difference than multiple seasons of reactive post-emergent spraying. Start the prevention program and stick to it.