How to Get Rid of Cogongrass: Smother-and-Slash Method That Stops Regrowth

How to get rid of cogongrass—this relentless invader chokes out native plants and ruins landscapes faster than you can say "wildfire." 🌱 After years of battling it, I finally cracked the code with the smother-and-slash method, which stops regrowth for good. The secret? Attacking it before it seeds while suffocating the roots to block new shoots.

This method works best in spring or fall when the grass is actively growing but not yet dormant. You’ll need a sharp shovel, heavy-duty black plastic, landscape fabric, and a few weeks of patience.

The process isn’t quick, but it’s far more effective than spot treatments or herbicides alone. Most gardeners quit too soon—stick with it for at least 6-8 weeks to see real results.

By the end of the season, you’ll have a weed-free zone where cogongrass once ruled. The soil stays healthier, native plants rebound, and you won’t spend another summer hacking at stubborn rhizomes.

The best part? This approach works in urban, rural, and wildland areas, making it a sustainable solution for any infestation.

Fair warning: cogongrass fights back hard. If you’re dealing with a large patch, consider professional help for the initial cleanup. But once you’ve smothered the roots, you’ll reclaim your land—permanently. Let’s get started with the step-by-step plan that actually works.

What you need

Step-by-step instructions for eliminating cogongrass

Here's the battle-tested approach I use to permanently remove this invasive grass—no regrowth, no second-guessing.

Cogongrass spreads aggressively, so timing matters. Wait until late summer or early fall when the plant is actively growing but before seed production. This is when the rhizomes (underground stems) are most vulnerable. Mow or cut the grass down to 1-2 inches above ground level—this weakens the plant and prevents seed dispersal.

I use a string trimmer or lawnmower for large areas, but for stubborn patches, I pull individual clumps by hand. You'll feel the resistance as you tug—this is the rhizome network at work. The goal is to remove as much of the plant as possible while leaving the roots exposed to sunlight and drying elements.

After cutting, cover the area with 6-12 sheets of thick cardboard or landscape fabric, overlapping edges by 6 inches. Secure the edges with rocks or heavy objects to prevent wind from lifting the cover. This blocks sunlight, which the cogongrass needs to photosynthesize and regrow.

Leave the cover in place for at least 6-12 months. You'll notice the area beneath the cover drying out and turning brown—this is the plant starving without light. If you see any green shoots poking through, cut them off immediately and replace the covering. Patience here is key; cogongrass is tough, but consistency wins.

Check the covered area every 2-4 weeks for signs of regrowth. If you spot any new shoots, trim them at the base and replace the covering. Over time, the cogongrass will exhaust its energy reserves, and the rhizomes will die off. This method works best in hot, dry climates where the soil stays consistently warm.

If the area is prone to heavy rain, add an extra layer of plastic sheeting over the cardboard to keep moisture out. Waterlogged conditions can actually encourage rhizome growth, so drainage is critical. After 12 months of no new growth, you can carefully remove the covering and test the soil for remaining roots.

Once the covering is removed, dig up the soil in the treated area to check for any remaining rhizomes. Look for white, fleshy roots—these are the cogongrass's survival mechanism. If you find any, remove them completely and dispose of them in sealed bags. Do not compost them, as even small pieces can regrow.

To prevent future invasions, maintain a healthy lawn or landscape in the surrounding area. Cogongrass thrives in disturbed or weak soil, so keeping your yard dense and competitive reduces its chances of returning. If you're in a high-risk zone, consider installing a root barrier around the perimeter of your property.

Tips & tricks for eliminating cogongrass effectively

This invasive grass won't surrender easily—here's how to tilt the battle in your favor with precision timing and smart tactics.

Timing is Everything: Late summer to early fall is your window because the plant's energy is focused on growth, not seed production. I've seen cogongrass bounce back when tackled in spring—wait until those warm, dry months when the rhizomes are most vulnerable. The 1-2 inch cut height is critical: shorter cuts expose more roots to sunlight, accelerating their demise.

Layering for Maximum Impact: Don't skimp on the covering—6-12 sheets of cardboard or landscape fabric creates a true light barrier. I've had success with black plastic sheeting too, but cardboard works better in rain-prone areas because it allows some drainage while still blocking light. The overlapping edges create a sealed system that prevents even the smallest shoots from escaping.

Rhizome Detection Pro Tip: When testing for remaining roots in Step 4, dig at least 6-8 inches deep—rhizomes can extend surprisingly far. I learned this the hard way after seeing regrowth from missed roots. Look for those white, fleshy stems; even small fragments can regenerate, so remove every trace you find.

Climate Adaptation: In cooler climates or during wet seasons, extend the covering period to 18 months. The 12-month minimum works best in hot, dry conditions where the soil stays warm. I've had to double the time in northern regions where moisture keeps rhizomes active longer. The key is maintaining that consistent suffocation of light.

Frequently asked questions

How long does it take to fully eradicate cogongrass?

Cogongrass is persistent, so expect at least 2–3 years of consistent smothering and slashing. The first year targets visible growth; subsequent years attack hidden rhizomes. Patience is key—skipping steps risks regrowth. Pro tip: Mark treated areas to avoid missing spots!

When is the best time of year to start?

Spring (March–May) is ideal—young shoots are easier to cut, and smothering materials work best before summer heat. Avoid winter: cold slows rhizome growth, but dormant plants are harder to locate. Action tip: Start in early spring, then repeat annually in late summer if needed.

Can I use herbicides instead of smothering?

Herbicides like glyphosate can work, but cogongrass resists spot treatments. For best results, combine herbicide with smothering/slashing. Follow label instructions precisely—overuse harms soil and nearby plants. Warning: Never spray during wind or rain to prevent drift.

What if cogongrass keeps coming back after treatment?

Regrowth usually means missed rhizomes. Dig deeper (12+ inches) to expose hidden roots, then smother again. Check these:

• Did you cover all visible stems?
• Is your barrier (cardboard/plastic) intact?
• Are you treating annually?

Is smothering expensive? Are there cheaper alternatives?

Smothering costs $20–$50 for materials (plastic sheets, mulch), but it’s cheaper long-term than herbicides. Budget hacks:

• Use free cardboard/newspaper under plastic.
• Repurpose old carpet or thick mulch.
• Check local compost programs for discounted mulch.

Wrapping up and next steps

Eradicating cogongrass is tough but doable with persistence! By combining the smother-and-slash method—like cutting, smothering with thick mulch, or solarizing—the roots will weaken over time. Stay consistent, monitor regrowth, and don’t hesitate to repeat treatments. You’ve got this!

Ready to reclaim your yard? Start by clearing the area this weekend, then set a reminder to check for new sprouts every few weeks. Small steps lead to big wins—your grass-free future is within reach! 🌱✨