What Do I Put On The Bottom Of A Raised Garden Bed
Deciding what to put on the bottom of a raised garden bed is one of those deceptively simple questions that gardeners argue about over coffee. After building dozens of beds over the years, I’ve learned there’s no single perfect answer — but there are clear choices depending on your site, budget, and the pests or drainage issues you face. In this article I’ll walk you through the best options, their pros and cons, and my honest recommendations based on real-world experience.
Why the bottom matters
The base of a raised bed controls drainage, weed pressure, and whether burrowing pests will raid your roots. It also influences how quickly the bed integrates with the ground and how easy the roots are for deep-rooted crops. Knowing your soil and pests will steer the decision.
“A little thought at the bottom saves a lot of trouble later.” — me, after wrestling with a vole invasion
Common options and when to use them
Cardboard or newspaper (my go-to for beds on grass)
This is the easiest, cheapest, and most gardener-friendly approach. Lay down a double layer of cardboard (remove tape and staples) or a thick stack of newspapers, then place the bed on top and fill with soil.
- Pros: Suppresses grass and weeds, biodegradable, lets earthworms through, cheap or free.
- Cons: Breaks down over a year or two, so it’s not a barrier to burrowing pests long-term.
My experience: I use cardboard for most backyard beds. It’s soothing to watch it decompose, feeding the soil and softening the barrier for roots.
Landscape fabric or geotextile (for controlled weed suppression)
Commercial landscape fabric provides a semipermeable barrier that slows weed growth while letting water drain.
- Pros: Long-lasting, reduces weeds, allows water to pass through.
- Cons: Can still allow thin-rooted weeds and grass to grow through edges; not great for worm flow; not recommended where you want rapid integration with native soil.
When I used fabric under a raised bed on a rental lawn, it kept grass at bay for several seasons and made removal easier when I moved.
Hardware cloth or wire mesh (must for gophers and voles)
If you live where gophers, voles, or moles are common, a galvanized hardware cloth (1/2 inch or 1/4 inch mesh) stapled to the bottom is the best defense.
- Pros: Blocks burrowing rodents without blocking water, durable for years.
- Cons: Adds cost and a bit of construction time; needs corrosion-resistant materials for longevity.
Pro tip: Cut the mesh to fit the bed and bend it slightly upward along the sides so pests can’t tunnel in along the edges. I’ve saved countless carrot and lettuce crops this way.
No barrier — direct contact with the ground
Sometimes the best option is nothing at all. Setting the bed directly on soil encourages roots to penetrate, improves drainage in clay-heavy yards, and allows soil biology to move freely.
- Pros: Encourages deep-root growth and microbial exchange, cheapest option, perfect for long-term beds.
- Cons: Weeds and grass can migrate in; burrowers can access roots.
I use no barrier for long-lived beds in my kitchen garden where I want tomatoes and comfrey roots to explore the subsoil. I accept more hand-weeding in exchange for healthier deep-rooted plants.
Gravel or coarse rock (only for beds on hard surfaces)
If you’re placing a bed on concrete, pavers, or decking, add a layer of coarse gravel or broken pottery for drainage before adding soil. Concrete won’t drain like native soil, so roots can sit in water if you skip this step.
- Pros: Improves drainage, prevents waterlogging on impermeable surfaces.
- Cons: Adds weight; not needed on permeable soils.
Layering recommendations for different situations
Raised bed on existing lawn or garden soil
- Lay down a double layer of cardboard or 6–8 sheets of newspaper to smother grass.
- Optional: Add a thin layer of finished compost or topsoil to encourage earthworms.
- Fill with your soil mix.
Raised bed on concrete or patio
- Place a weed fabric to protect the surface, then 2–3 inches of coarse gravel for drainage.
- Optionally line with a breathable fabric to keep soil from washing into the gravel.
- Fill with soil mix.
Raised bed in vole/gopher country
- Line the bottom with galvanized hardware cloth with half-inch mesh, fastening it to the frame.
- Cover with a thin layer of cardboard to suppress weeds, then add soil.
Materials to avoid
- Thick plastic sheeting directly under the soil — it blocks drainage and starves the soil of beneficial life.
- Old treated lumber scraps that are rotting and contaminated — always use rot-resistant or untreated wood that’s safe for vegetable production.
Practical tips from my garden
I once skipped hardware cloth and lost a bed of beets to gophers in a single night — that taught me the value of a mesh barrier. On the other hand, cardboard beds became my favorite lazy-bed method: plant, mulch, and let the cardboard turn into compost over a season.
When building on a patio, adding gravel transformed soggy cucumber beds into vigorous producers. And I always recommend shallow trenches around the frame to tuck in cardboard edges — it keeps grass from slipping underneath.
Quick decision guide
- If you’re on grass and want easy setup: cardboard or newspaper.
- If you’re on concrete: gravel plus drainage fabric.
- If you have burrowing pests: hardware cloth under the bed.
- If you want long-term soil integration: no barrier; set the frame directly on soil.
Final recommendation
There’s no single “right” answer, but here’s what I use most: cardboard for beds on lawn, hardware cloth under any beds in pest areas, and no barrier for permanent beds where I want deep roots. Combine these basics with good soil and drainage and you’ll have a productive bed that feels like home to roots and worms alike.
Gardening is about adapting to your land. Try one approach, observe, and tweak the next season. Your raised bed will thank you with strong, healthy plants.
