Will Roundup Kill Prickly Pear Cactus

Roundup will kill prickly pear cactus, but it often takes multiple applications and a surfactant to be truly effective.
 
Many homeowners wonder if Roundup can kill prickly pear cactus when they spot those spiny pads spreading across their yard.
 
The short answer is yes, Roundup can kill prickly pear cactus, though the process is slower and more stubborn than killing typical weeds.
 
Prickly pear cactus has a thick, waxy skin that resists herbicides, so Roundup will kill prickly pear cactus best when you cut or score the pads first.
 
In this post, we’ll dig into how Roundup kills prickly pear cactus, the best application methods, and why you might need a few rounds of treatment.
 
Let’s get started so you can reclaim your landscape from these tough desert invaders.
 

How Roundup Kills Prickly Pear Cactus

Roundup will kill prickly pear cactus when the active ingredient glyphosate gets absorbed into the plant’s vascular system.
 
Once absorbed, glyphosate travels down to the roots and disrupts the cactus’s ability to produce essential amino acids.
 
The cactus slowly starves and dies over a few weeks, but the waxy coating of prickly pear pads makes absorption tricky.
 
Here’s a closer look at what makes Roundup effective on prickly pear cactus and where it falls short.
 

1. The Waxy Skin Barrier

Prickly pear cactus has a thick, waterproof cuticle that keeps water from evaporating and also keeps herbicides out.
 
This means Roundup will kill prickly pear cactus only if you break through that barrier.
 
Simply spraying the pads often results in the liquid beading up and rolling off like rain on a car hood.
 
To get Roundup to kill prickly pear cactus, you’ll want to add a surfactant to help the solution stick and penetrate.
 
You can also score the pads with a knife to create entry points for the herbicide.
 

2. Cutting the Pads First

One proven way to ensure Roundup will kill prickly pear cactus is to cut the pads off and then paint the cut surface with herbicide.
 
When you slice into the fleshy pad, you expose the inner tissue where glyphosate can be readily absorbed.
 
Use a concentrated Roundup solution and apply it directly to the fresh cut within minutes of slicing.
 
This method is much more reliable than foliar spraying because it bypasses the waxy exterior altogether.
 
Some folks even chop the entire cactus down to the base and treat the stump, just like you would with a tree.
 

3. Timing Matters for Absorption

The best time to apply Roundup to prickly pear cactus is during active growth in late spring or early summer.
 
During this period, the cactus is moving nutrients and water through its system, which helps carry the herbicide down to the roots.
 
If you spray during winter dormancy, Roundup will kill prickly pear cactus much slower or may not work at all.
 
A warm, dry day with no rain forecast for 24 hours is ideal for application.
 
Rain within a few hours will wash the herbicide off before it can penetrate.
 

Why Roundup Might Not Kill Prickly Pear Cactus on the First Try

Many folks spray once and wonder why the cactus looks fine weeks later.
 
This happens because Roundup will kill prickly pear cactus only when it gets into the plant in sufficient quantity.
 
Prickly pear cactus has an extensive root system with energy reserves that can fuel regrowth even after top growth dies.
 
Here are the most common reasons Roundup fails on prickly pear cactus and what to do about it.
 

1. Incomplete Coverage

If you spray only lightly, the herbicide won’t reach enough living tissue to kill the entire root system.
 
You need to thoroughly wet every pad and joint where new growth emerges.
 
Missed spots will continue to grow and eventually produce new pads after the treated areas die off.
 
Reapply after two to three weeks to catch any survivors and prevent the prickly pear cactus from bouncing back.
 

2. Using Too Dilute a Mixture

Roundup comes in various strengths, and the ready-to-use formulas are often too weak for hard-to-kill plants like cactus.
 
For prickly pear cactus, use a concentrate at a higher rate than you would for annual weeds.
 
A 2% to 5% glyphosate solution is a good starting point for prickly pear cactus.
 
Mix it with a non-ionic surfactant at the label rate to maximize absorption.
 
Always read the product label for specific mixing instructions for woody or succulent plants.
 

3. Regrowth from Root Fragments

Even if Roundup kills the main prickly pear cactus plant, any root pieces left behind can sprout new cactus.
 
If you physically remove the cactus first, make sure you dig out as much of the root system as possible.
 
Then apply Roundup to any regrowth that emerges to exhaust the roots’ energy reserves.
 
Follow-up applications are essential to fully kill prickly pear cactus over the long term.
 

Alternative Methods to Kill Prickly Pear Cactus

If Roundup isn’t doing the job or you prefer not to use chemicals, there are other ways to kill prickly pear cactus.
 
These methods can work alongside or instead of Roundup to control the spread.
 

1. Physical Removal

Digging up the entire cactus including the roots is the most immediate way to kill prickly pear cactus.
 
Use a shovel or a pickaxe to loosen the soil around the base before pulling.
 
Wear thick leather gloves and use tongs or a grabber to handle the spiny pads safely.
 
Dispose of the cactus pieces in a sealed bag or burn them to prevent rooting from discarded pads.
 

2. Smothering with Tarps

Another non-chemical option is to cover the prickly pear cactus with a thick black plastic tarp.
 
This blocks sunlight and traps heat, slowly cooking the cactus over several months.
 
It’s slow but effective, and you don’t have to worry about herbicide runoff or drift.
 
Weigh down the tarp edges with rocks or soil so the cactus can’t push through or escape.
 

3. Fire or Heat Treatment

Some ranchers use propane torches to burn prickly pear cactus, which can kill the top growth and eventually the roots.
 
This method is risky and not recommended near structures or dry grass.
 
If you try it, be prepared for multiple passes over several weeks to fully exhaust the plant.
 
Burning alone rarely kills the root system on the first attempt, so combine it with Roundup for better results.
 

So, Will Roundup Kill Prickly Pear Cactus?

Roundup will kill prickly pear cactus, but you need patience and proper technique.
 
It’s not a one-and-done spray like killing dandelions in your lawn.
 
The waxy pads and deep roots demand a more strategic approach, whether that’s cutting and painting or repeated foliar applications with a surfactant.
 
If you follow the steps we’ve outlined, Roundup will kill prickly pear cactus and keep it from coming back.
 
Remember to treat during active growth, use a strong enough concentration, and stay on top of regrowth for a few months.
 
With persistence, you can eliminate prickly pear cactus from your property and enjoy a spine-free landscape.
 
So grab your Roundup, a good surfactant, and start tackling that prickly pear cactus today.