What to Put Under a Raised Garden Bed? And what to avoid.

"What should I put under my raised bed?"It's usually the first question new gardeners ask.

Short answer?

It depends on what's already there. Let's keep this practical.

 

1. Building Over Grass? Smother First.

This is the most common scenario in backyards. If you're placing your bed directly over lawn, don't skip this step.

Here's what I do:

Remove thick perennial weeds organically if needed

Lay down plain brown cardboard (no glossy coating)

Overlap seams

Wet thoroughly

Build and fill on top

The cardboard smothers grass and breaks down naturally over time. Worms move in. Soil life connects. The lawn underneath fades away. Simple. Effective. No plastic required.

 

2. Building Over Bare Soil? Keep It Open.

If you're placing your bed directly on native soil, you usually don't need anything underneath.

Open contact allows:

Better drainage

Deeper root growth

Earthworms to migrate upward

Raised beds aren't containers. They're extensions of your soil.

Unless you're solving a specific problem, keep it simple.

 

3. What About Gophers, Moles, and Burrowing Pests?

Yes—this is very common in many parts of the U.S.

Gophers are common in the West and Midwest. Moles are widespread and tunnel under lawns. Voles can chew roots. If you've seen tunnels, raised soil lines, or plants collapsing from below, hardware cloth makes sense.

Attach galvanized hardware cloth (½ inch mesh) to the bottom of the frame before filling.

It allows drainage. It blocks rodents.

 

4. What I Avoid (And Why)

❌ Plastic Sheeting

Blocks drainage.

Blocks soil life.

Traps water.

Not helpful in food beds.

❌ Thick Landscape Fabric Inside the Bed

Over time, roots clog it.

Soil compacts.

Weeds still grow on top.

Save it for pathways if you use it at all.

❌ Treated Lumber Scraps

Modern pressure-treated wood is safer than decades ago, but I still avoid burying questionable materials in food beds.

If I wouldn't add it to compost, I don't add it under vegetables.

Before putting anything underneath, ask:

Are you blocking grass?

Stopping burrowing animals?

Improving drainage?

Preventing weeds from below?

Solve the problem you actually have—not every possible problem you've read about online.

Gardening is rarely about eliminating every risk. It's about adjusting. You learn your climate. You learn your soil. You learn which animals visit at night. You solve what needs solving. And you let the rest be. Some seasons are smoother than others. Some creatures outsmart you.

And honestly?

That's part of it.

The best gardens aren't built perfectly. They're built thoughtfully—and adjusted season by season.

Start simple.

Then let your backyard teach you the rest.

 

You may also enjoy these related blogs:

Using Cardboard in the Garden: What It Really Does to Your Soil