Barrier materials stop weeds and keep soil in place
The ground around your raised bed needs a barrier to prevent weeds from creeping in and to keep mulch or soil from washing away. The most common choices are landscape fabric, cardboard, wood chips, and gravel — each works differently and lasts a different length of time. What you choose depends on how much foot traffic the area gets, whether you want something you can walk on, and how often you're willing to replace it.
A barrier also protects the soil inside your bed from compacting under rain and foot traffic. Without one, the ground around the bed becomes hard and weedy, and you end up spending more time weeding than growing. The right barrier material does most of that work for you.
Key Takeaways
- Landscape fabric blocks weeds while letting water through, and lasts three to five years before it breaks down.
- Cardboard is free or cheap, biodegrades in one to two years, and works best under wood chips or mulch.
- Wood chips and bark mulch suppress weeds, improve soil as they decay, and need replacing every two to three years.
- Gravel and stone don't decay but can trap heat and make weeding harder if you need to pull anything that does grow through.
- Combining two materials — cardboard under wood chips, for example — gives you longer protection and better weed control.
Landscape fabric: the long-lasting option
Landscape fabric is a woven or non-woven synthetic material that blocks weeds while allowing water and air to pass through. It typically lasts three to five years before UV light and foot traffic break it down. You lay it flat on the ground around the bed, overlap the edges by at least 6 inches, and pin it down with landscape staples or rocks.
The main advantage is durability — you won't need to replace it as often as mulch. The main drawback is that it's visible unless you cover it with something else, and if you do cover it, you're adding another material anyway. Landscape fabric also makes it harder to add organic matter to the soil around the bed, since you can't straightforward turn fallen leaves into the ground.
If you use landscape fabric, buy the kind rated for at least five years of outdoor use. Cheap thin fabric tears easily and won't last. Overlap seams generously and weight down the edges so weeds don't find gaps to push through.
Cardboard: the free or nearly free choice
Cardboard is one of the cheapest barriers you can use. Flatten boxes from deliveries or ask a grocery store for their produce boxes — most will give them away. Lay the cardboard flat on the ground, overlap pieces by at least 6 inches, and wet it down so it stays in place. It will start to break down within a few months and be mostly gone within one to two years.
Cardboard works best when you cover it with wood chips or mulch, which holds it in place and hides it. Without a cover, it looks messy as it degrades and can blow around in wind. The upside is that as it breaks down, it adds organic matter to the soil, which improves drainage and structure over time.
Use plain cardboard only — avoid anything with plastic tape, glossy printing, or wax coating. Wet the cardboard thoroughly before laying it down, and make sure it's in full contact with the soil so weeds can't find air pockets to grow through.
Wood chips and bark mulch: weed suppression plus soil building
Wood chips and bark mulch do double duty: they block weeds and, as they decay, they add organic matter to the soil. Spread them 3 to 4 inches deep around the bed. They'll suppress most weeds, though some hardy ones may still push through. Every two to three years, add another layer as the original breaks down.
The main advantage is that they improve soil as they decay, making the ground around your bed richer and easier to work with over time. The disadvantage is that you have to replace them regularly, and they can attract termites or carpenter ants if they're in contact with wooden structures like house siding or deck posts. Keep mulch at least 6 inches away from wood.
Use arborist chips (free wood chips from tree removal companies) or purchased bark mulch. Avoid dyed mulch unless you know what dye was used — some contain chemicals you may not want near your garden. Avoid fresh wood chips from conifers, which can tie up nitrogen in the soil as they decay.
Gravel and stone: permanent but with tradeoffs
Gravel and stone don't decay, so they last indefinitely. Spread them 2 to 3 inches deep. They suppress weeds reasonably well, though some seeds will still germinate in the small spaces between stones. Gravel is cheaper than decorative stone but can scatter into the bed or onto paths.
The downsides are significant: gravel and stone absorb and hold heat, which can dry out the soil around your bed faster than you'd like. They also make it harder to pull weeds if any do grow through, since you have to dig through the stone to get to the root. Over time, gravel works its way into the soil and becomes hard to remove if you change your mind.
If you use gravel, lay landscape fabric underneath it to slow weed growth and make it easier to rake the gravel away later if needed. River rock and pea gravel are easier to walk on than sharp crushed stone.
Combining materials for better results
Many gardeners use two materials together for better weed control and longer-lasting protection. The most common combination is cardboard or landscape fabric underneath, with wood chips or mulch on top. The fabric or cardboard blocks most weeds, and the mulch hides the barrier and adds organic matter as it decays.
Another option is landscape fabric with gravel on top. This gives you the durability of fabric with a finished look and permanent coverage. The gravel won't decay, so you won't need to add more, but you'll still need to rake it occasionally to keep it even.
A three-layer approach — cardboard, then landscape fabric, then wood chips — gives you the longest weed suppression and the most organic matter added to soil, but it's overkill for most home gardens. Two layers is usually enough.
How to install barriers correctly
Start by clearing away any existing weeds and debris from the ground around the bed. Rake it relatively smooth — you don't need it perfect, but big lumps will create gaps where weeds can sneak through. If the ground is very hard or compacted, water it first to soften it.
Lay your first material (cardboard or fabric) flat on the ground, starting at the edge of the bed and working outward. Overlap seams by at least 6 inches — this is the most common place weeds find their way through. Pin or weight down the edges so wind and foot traffic don't shift it. If you're using cardboard, wet it thoroughly so it stays in place and makes good contact with the soil.
If you're adding a second material like mulch or gravel, spread it evenly over the barrier, keeping it at least 6 inches away from the wooden frame of the bed itself. This prevents rot and pest problems. Rake it smooth and add more as it settles.
Frequently Asked Questions
Can I use plastic sheeting instead of landscape fabric?
Plastic sheeting blocks weeds but also blocks water, which means rain pools on top and roots can't access moisture from below. Landscape fabric is better because it lets water through. If you use plastic, you'll need to cut holes or slits to let water reach the soil, which defeats the purpose of having a continuous barrier.
How often do I need to replace the barrier?
Cardboard lasts one to two years. Wood chips and mulch last two to three years before they break down enough that you need to add more. Landscape fabric lasts three to five years. Gravel and stone don't need replacing unless they scatter away or work into the soil.
What if weeds still come through?
Weeds can push through any barrier if it has gaps or if seeds land on top of mulch and germinate there. Pull them by hand when they're small, before they establish roots. If you're getting a lot of weeds, your barrier probably has gaps — check the seams and add more mulch or fabric to problem areas.
Should I remove the barrier at the end of the season?
No. Leave it in place year-round. It protects the soil in winter and prevents weeds from establishing before spring. If you're using cardboard or mulch, it will be breaking down anyway and adding organic matter to the soil, which is beneficial.
Can I use leaves as a barrier?
Leaves alone won't work as a barrier because they blow around and break down too quickly. But you can use them as a top layer over cardboard or fabric. Shredded leaves work better than whole leaves because they pack down and stay in place longer.