A Landscaper’s Perspective on Cardboard, Bark & Landscape Fabric
If you order anything online, there’s a good chance you have cardboard boxes sitting around your house.
Amazon boxes.
Costco boxes.
Moving boxes.
Shipping boxes.
Eventually, someone looks at that pile of cardboard, looks at the blackberry or weeds growing in the backyard, and has an idea:
Why don’t I put the cardboard over the weeds and cover everything with bark?
That’s essentially sheet mulching.
And yes, cardboard can be used as part of a sheet-mulching system.
But if you’re dealing specifically with established Himalayan blackberry, there’s an important distinction:
Something can work biologically without necessarily being the most practical way to build a finished landscape.
From a contractor’s perspective, that’s where cardboard becomes complicated.
Will Cardboard Kill Blackberry?
It can help suppress blackberry growth, particularly after the existing canes have been cut down.
Cardboard blocks sunlight and creates a temporary physical barrier underneath mulch.
But established blackberry isn’t just what you see above ground.
There’s also a crown and root system underneath.
If you simply cut mature blackberry down, put cardboard over it, and assume the problem is permanently solved, you may be disappointed.
Blackberry can send new growth around weak points, edges, gaps, and other openings, and remaining plants can require follow-up control.
That’s why our preferred starting point for a major blackberry restoration is usually:
Cut the canes.
Remove accessible crowns and roots where appropriate.
Clean the area.
Then decide how the ground should be managed afterward.
Cardboard, mulch, fabric, planting, or continued maintenance comes after that decision.
What Is Sheet Mulching?
At its simplest, sheet mulching means covering existing ground with overlapping material—commonly cardboard—and then covering that with organic material such as arborist chips or mulch.
The cardboard temporarily reduces light and creates a barrier between the existing surface and the mulch above.
Over time, plain cardboard breaks down.
That’s part of its appeal.
It’s inexpensive.
Many homeowners already have it.
And unlike permanent synthetic fabric, it eventually decomposes into the landscape.
For certain garden projects, that can be very useful.
But that doesn’t mean it’s ideal for every property.
The Contractor Problem: Scale
Imagine sheet mulching a small 4-by-8-foot garden area.
That’s pretty manageable.
Now imagine doing 1,000 square feet.
Or 2,000 square feet.
Suddenly you need a lot of cardboard.
It needs to be prepared.
Tape, labels, staples, and other non-cardboard material may need to be removed.
Pieces need to overlap appropriately.
The cardboard needs to follow the ground.
Then everything needs to stay where you put it while you’re installing mulch over the top.
Now add:
A slope.
Tree roots.
Rocks.
Uneven soil.
Remaining shrubs.
Irrigation.
Edges.
Fences.
Existing plants.
Blackberry crowns.
That’s when something that sounds incredibly simple starts consuming a surprising amount of labor.
The Ground Still Has to Be Prepared
This is probably the part homeowners underestimate most.
Suppose the ground looks like this:
Blackberry was just removed.
There are holes where crowns were excavated.
There are rocks.
There are roots.
There are little mounds of soil.
There are depressions.
There are branches and debris.
Throwing cardboard over all of that doesn’t make the ground flat.
Then you install three inches of mulch.
The mulch follows much of what’s underneath it.
If you want a finished residential landscape to look clean, some preparation still matters.
You may need to remove debris.
Fill depressions.
Knock down high areas.
Establish reasonable grades.
Clean the edges.
Work around existing plants.
Then install the covering material.
Cardboard doesn’t eliminate site preparation.
It adds another installation layer.
Why Contractors May Prefer Simpler Systems
Professional landscaping has another consideration:
labor.
Suppose I have several crew members on a property.
Every additional step costs time.
Collect cardboard.
Prepare it.
Move it around the property.
Lay it out.
Overlap it.
Keep it positioned.
Work it around obstacles.
Then install mulch.
If the homeowner is doing the work themselves with cardboard they already have, that extra labor may effectively cost them nothing except their Saturday.
For a contractor, Saturday isn’t free.
The customer is paying for every additional labor hour.
That’s where we have to ask:
Is the additional step producing enough benefit to justify the additional labor?
Sometimes the answer may be yes.
Sometimes it isn’t.
What About Landscape Fabric?
Landscape fabric is another option, but it has its own tradeoffs.
A commercial roll is consistent in size and thickness.
It can be rolled across a prepared area relatively quickly.
It conforms reasonably well to the ground.
It can be cut around obstacles.
It can be secured with staples and covered with mulch or another appropriate material.
For contractors working across a large area, that consistency can make installation substantially easier than assembling hundreds of individual cardboard boxes.
But landscape fabric isn’t perfect either.
It’s a synthetic product.
Organic material can accumulate on top of it.
Weeds can eventually germinate in that material.
Persistent plants may find openings and edges.
Fabric can become exposed.
Roots can interact with it.
And if someone wants to renovate the bed years later, old fabric can become something they have to deal with.
So I wouldn’t describe landscape fabric as the universal answer.
It’s another tool.
There are situations where we may use it and situations where I would rather not.
What About Just Using Mulch?
This is often the simplest option.
Remove the unwanted vegetation as thoroughly as reasonably practical.
Prepare the area.
Then install an appropriate layer of mulch.
Mulch helps cover exposed soil and reduce weed pressure.
It also creates a clean visual surface.
But mulch doesn’t make weeds impossible.
Organic mulch decomposes.
Leaves fall onto it.
Seeds land on it.
Blackberry or other persistent plants can return.
Eventually the area needs maintenance.
That’s landscaping.
There is rarely a material you install once that permanently eliminates every future weed.
Cardboard Has One Major Advantage
There is something I genuinely like about cardboard:
It’s accessible.
If you’re a homeowner doing the project yourself, you may already have everything you need.
You can save boxes for a few months.
Break them down.
Prepare the area.
Lay them out.
Cover them with mulch.
And see how it performs.
For a DIY garden project, the economics can make a lot of sense because you’re contributing the labor yourself.
You aren’t paying a crew to spend hours preparing and fitting cardboard across the property.
That’s an important difference.
Something that doesn’t make economic sense for a contractor can still make perfect sense for a homeowner.
Where I Think Cardboard Makes the Most Sense
I like the idea more for relatively manageable areas where:
The ground can be prepared reasonably well.
The homeowner already has cardboard.
The area isn’t extremely complicated.
The homeowner is willing to spend the installation time.
The finished surface will receive enough mulch to cover the cardboard properly.
And the homeowner understands that future maintenance will still be required.
I like it less when we’re dealing with a huge, irregular blackberry restoration where speed, consistency, appearance, and labor efficiency become major considerations.
That’s where the economics start changing.
Blackberry Changes the Equation
This article is specifically about blackberry, and that’s important.
Sheet mulching ordinary weeds in a garden bed isn’t necessarily the same problem as managing a mature blackberry infestation.
If blackberry has occupied an area for years, there may be substantial crowns and roots underneath the visible canes.
That’s why I don’t like treating cardboard as the blackberry-removal method itself.
Think of it as something that may be used after the initial clearing as part of the next phase.
The first question is:
How thoroughly are we removing or controlling the existing blackberry?
The second question is:
What do we want this area to become?
Those answers should determine what goes on top afterward.
You Don’t Need a Perfect Weed Barrier
This is one of the larger lessons I’ve learned working in landscaping.
Homeowners frequently look for the product that will stop weeds forever.
Cardboard?
Landscape fabric?
Six inches of bark?
Gravel?
Plastic?
There usually isn’t a perfect answer.
Landscapes are living systems.
Soil moves.
Mulch decomposes.
Seeds arrive.
Plants spread.
Leaves accumulate.
Roots grow.
The objective shouldn’t necessarily be:
How do I make sure another weed never appears here?
A more practical question is:
How do I make this area easier to maintain?
That’s a much more achievable goal.
So, Does Cardboard Work?
Yes.
Cardboard sheet mulching can be a useful way to suppress vegetation and cover soil, particularly for homeowners willing to do the work themselves.
But I wouldn’t treat cardboard as a guaranteed solution for established blackberry.
And from a professional contractor’s perspective, it isn’t always the most efficient material for a large landscape.
Preparing and fitting hundreds of pieces of cardboard across uneven terrain can consume a significant amount of labor.
Landscape fabric can be faster and more consistent in some applications, but it introduces synthetic material and has its own long-term disadvantages.
Mulch alone is simpler, but it also requires ongoing maintenance.
There is no perfect system.
That’s the real answer.
If you already have a pile of plain cardboard, a manageable area, and a free Saturday?
Try it.
Prepare the ground properly.
Overlap the cardboard.
Cover it thoroughly.
Monitor the area.
See how it performs.
But if you’re staring at 2,000 square feet of mature blackberry on a Seattle hillside, don’t expect a stack of Amazon boxes to magically solve the underlying problem.
Clear the blackberry first. Decide what you want the land to become second. Then choose the ground-cover system that makes sense for that goal.