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Roundup will kill blackberry bushes when it’s applied correctly and at the right time.
But whether it actually finishes the job depends on how you use it and how established those bushes are.
If you’ve been asking will Roundup kill blackberry bushes, the short answer is yes, though blackberries are tough and often need more than one application.
In this post, we’ll look at how Roundup kills blackberry bushes, when to spray them, and what to do about those stubborn regrowth shoots.
Will Roundup Kill Blackberry Bushes?
Roundup will kill blackberry bushes because its active ingredient, glyphosate, is absorbed through the leaves and carried down into the roots.
Here’s why it works so well on these stubborn plants.
1. Glyphosate Travels to the Roots
Glyphosate doesn’t just burn the leaves you spray.
Once it lands on healthy foliage, the plant absorbs it and moves it through its system all the way down to the root crown.
That’s the part that matters most with blackberries, since cutting the canes alone rarely kills them.
2. It Disrupts the Plant’s Growth System
Inside the plant, glyphosate blocks an enzyme that blackberries need to build proteins.
Without that enzyme, the bush can’t grow or repair itself, so it slowly shuts down.
You won’t see instant results, but the damage is happening below the surface.
3. Blackberries Are Sensitive to It
Blackberry bushes don’t have much natural tolerance for glyphosate.
That sensitivity is why Roundup can kill blackberry bushes effectively when it’s applied properly.
The catch is that blackberries spread through underground rhizomes, so any root pieces left untouched can send up new growth.
4. Timing Affects the Outcome
Roundup works best when blackberry bushes are actively growing and moving nutrients toward their roots.
Spray when the plant is putting energy downward, and the glyphosate rides right along with it.
Spray when the bush is dormant, and you’ll get a much weaker result.
How to Use Roundup to Kill Blackberry Bushes
Using Roundup on blackberry bushes takes a bit of patience and planning.
Follow these steps to give yourself the best shot at killing them for good.
1. Spray at the Right Time of Year
Late summer and early fall are usually the best times to spray blackberry bushes.
At that point, the plant is still actively growing but starting to store energy in its roots, which helps the glyphosate travel deeper.
Avoid spraying during drought, extreme heat, or when rain is expected within a few hours.
2. Apply to Healthy, Mature Leaves
Roundup needs to land on healthy, fully developed leaves to be absorbed.
New growth and damaged foliage won’t take it in as well, so target the mature leaves.
Spray until the leaves are wet but not dripping, and avoid drenching the soil around the bush.
3. Don’t Cut the Canes First
It’s tempting to chop blackberry canes down before spraying, but hold off.
The leaves are your delivery system for the glyphosate, so cutting them removes the plant’s ability to absorb the herbicide.
Spray first, then wait before you do any cutting.
4. Wait Before You Clear the Dead Canes
After spraying, give the bush a couple of weeks to start dying back.
Once the canes are brown and brittle, you can cut them down and clear the area.
Just don’t rush this step, because the herbicide needs time to work its way through the whole plant.
5. Repeat the Treatment as Needed
One application often isn’t enough to kill a mature blackberry bush completely.
Watch for new shoots sprouting from the roots or rhizomes, and respray those when they’re actively growing.
A second or third round of Roundup is usually what finally gets the job done.
Why Blackberry Bushes Keep Coming Back
Blackberry bushes are resilient because of how they spread underground.
Their root system and rhizomes store energy that lets them bounce back after a single spray.
That’s why some people spray, see the canes die, and then get frustrated when new growth appears weeks later.
The key is to stay consistent and hit the regrowth while it’s small and vulnerable.
You can also combine Roundup with other methods, like digging out the root crown or smothering the area with a thick mulch or tarp.
Combining approaches often works better than relying on Roundup alone, especially for large, established patches.
Safety Tips When Using Roundup
Always wear gloves, long sleeves, and eye protection when handling Roundup.
Keep pets and kids away from the treated area until it’s fully dry.
And be careful around desirable plants, since glyphosate will damage or kill anything it touches.
So, Will Roundup Kill Blackberry Bushes?
Roundup will kill blackberry bushes because glyphosate travels from the leaves down into the roots and shuts the plant down from the inside.
It won’t always happen in one spray, and those underground rhizomes can send up new shoots if you stop too soon.
Spray when the bushes are actively growing, apply to healthy leaves, and repeat the treatment until the regrowth stops appearing.
Hope this post has helped you understand whether Roundup will kill blackberry bushes and how to use it effectively.