The Dirt on Raised Bed Bottoms: What to Lay Underneath for Your Best Garden Yet

Great! You’re all set to construct that wonderful elevated garden bed. Especially if your native soil isn’t quite perfect or you’re seeking for simpler access, raised beds are really a great option to cultivate tasty vegetables, lovely flowers, or fragrant herbs. They provide so many advantages! But a very typical and crucial issue unavoidably arises as you draw up your plans and collect your supplies: what, if anything at all, should go on the bottom of a raised garden bed?

Okay, let’s get started! The straightforward response is: your particular bed objectives and the state of your garden will determine! No one answer fits all people. From delightfully porous materials like cardboard or newspaper for efficient weed control, to strong wire mesh for repelling burrowing pests, or even deciding to put nothing at all on the bottom if your bed is deep enough and it’s being placed on appropriate ground, common choices vary.

Selecting the appropriate (or no) bottom layer for your raised bed can greatly affect weed pressure control, avoidance of annoying pest issues, and even help of your soil’s general health down the line. This all-inclusive book will explore all the common options US gardeners think about, methodically assess their advantages and disadvantages, and assist you in determining what is really ideal for establishing a successful and fruitful basis for your garden. Let’s investigate it further!

Why Even Think About a Bottom Layer? The Possible Benefits for Your Raised Bed

First of all, not every single raised garden bed has to have something at the bottom. Many effective raised beds are constructed directly on the ground without any liner. On the other hand, there are some quite excellent and sensible justifications for why you could decide to include a particular layer before you fill it with that beautiful soil.

Some of the main possible advantages are as follows:

• Weed Warfare: A Major Advantage! Often, this is the main drive. A bottom barrier can be a whole game-changer if your raised bed is being constructed on top of an existing grass or a weedy area. It saves you a lot of weeding troubles later on by helping to stop stubborn grass or persistent weeds from your current lawn from sprouting up and infiltrating your lovely raised bed soil.
• Pest Blockade: Consider gophers, moles, or voles. A strong bottom layer, such as hardware cloth, may be your greatest defense if these tenacious pests are a frequent issue in your US area. It literally stops them from digging up from underneath and devouring the soft roots of your plants or upsetting your soil.
• Soil Retention: Especially during heavy rains or deep watering, a liner can help keep your precious, nutrient-rich soil mix from washing out or eroding if your raised bed frame has some larger gaps at the bottom (maybe between rustic wood planks) or if you’re placing your bed on a noticeable slope.
• Improving Drainage (In Specific Cases, and with Caution!): This one can be a bit counterintuitive for some materials, but in certain specific setups – for example, if your raised bed is being placed on extremely compacted clay soil that drains very poorly – some gardeners might use a very coarse material at the very bottom (below a permeable fabric) to try and create a drainage channel. But this calls for close attention since sometimes placing a layer of gravel under regular soil could impede drainage (more on this later!).
• Supporting No-Dig Gardening: For people who follow no-dig gardening techniques, piling materials like cardboard at the bottom of a new raised bed is a fundamental step. All without you having to perform any heavy digging to clear the area first, it helps to smother the current plant (grass and weeds) beneath, allowing it to degrade in place and contribute organic matter to the soil over time.

Depending on the difficulties of your garden, a bottom layer may provide some quite interesting advantages even if it is not always required.

Deciding What Lies Under Your Raised Garden Bed: Important Considerations

It’s really smart to pause and consider your particular requirements and the state of your garden before you run out and grab the first material you can find to line the bottom of your new raised bed. These inquiries have answers that will enable you to select the most suitable and efficient solution:

What is your bottom layer main goal?

• Are you mostly trying to prevent aggressive, hard-to-kill plants like Bermuda grass, quackgrass, or bindweed from entering from below?
• Do burrowing pests such as gophers, voles, or moles ruin your gardening in your region?
• Are you mostly worried about your nice soil mix washing away on a slope or slipping through frame openings?
• Are you trying to build a no-dig bed and suffocate current plants instead? Your best option will much depend on your main goal.

What Lies Beneath Where the Bed Will Go?

• Will your raised bed sit on top of an existing grass, an area of tenacious weeds, bare soil, or even an impermeable surface such as concrete or a patio?
• How good is the native soil underneath? Is it bad draining, compacted clay? Is it quick-draining and quite sandy? Or is it a good loam that you could wish your plant roots to one day link with?

How Deep Will Your Raised Garden Bed Be?

• If underlying vegetation is a major concern, shallower raised beds (say, less than 10-12 inches deep) can benefit more from a specific weed barrier as plant roots will be closer to that contact.
• Though it could still be required for pests, deeper beds (12 inches, 18 inches, or more) allow plant roots far more room to develop above any barrier and can occasionally render a bottom liner less important for weed suppression from below.

What Are You Planning to Plant in the Bed?

• Common bottom liners will suit most annual flowers, herbs, and veggies just great. On the other hand, if you intend to cultivate plants with extremely deep or aggressive root systems (like some large heirloom tomatoes, asparagus, or certain perennial shrubs), you should make sure any barrier you use is either permeable enough for roots to finally pass through (like decomposing cardboard) or that your bed is deep enough to support their complete root development above the barrier.

How Do Local Pest Pressures Compare (US Specific)?

• For many US gardeners, this is a major concern. Do gophers frequently appear (and cause issues) in your state or county? Do voles make harmful tunnels in your area? Does mole activity happen often? Your responses here will significantly determine whether investing in something robust like hardware cloth is a need or an optional precaution.

Considering these factors will help you choose the most reasonable and efficient option for your particular raised garden bed.

Common Bottom Options for Raised Garden Beds: Advantages, Disadvantages & Best Uses

Alright, let’s look at the most often used materials US gardeners think about for the bottom of their elevated beds. We’ll examine what each one provides in a fair manner—the excellent, the not-so-good, and when it could be the best fit.

Newspaper or cardboard (The Recycler’s Choice – Excellent for Weeds!)

This is a really common, environmentally friendly, and sometimes free choice!

Advantages:

• Readily Available & Cheap (or Free!): Most of us have stacks of newspaper or cardboard boxes on hand.
• Biodegradable & Soil-Improving: Over time—usually 1 to 2 seasons depending on thickness and moisture—cardboard and newspaper will break down and compost, so enriching your soil with useful organic matter.
• Great for Smothering Grass and Weeds (Sheet Mulching): Cardboard particularly excels here. A thick, overlapping covering effectively blocks sunlight, smothering existing grass and weeds under your new bed, therefore providing a wonderful no-dig beginning.
• Permeable (Eventually): Though it may be a barrier at first, permeable eventually lets water drain through and promotes the movement of earthworms and good soil bacteria between your raised bed soil and the ground below as it softens and decomposes.

Drawbacks:

• Temporary Solution: It’s not a permanent remedy for particularly aggressive perennial weeds (they might ultimately find their way back) or for burrowing bugs as it breaks down.
• Can Initially Harbor Slugs: Slugs and snails may occasionally find the damp, gloomy surroundings beneath fresh cardboard to be appealing hiding place. As the cardboard begins to decompose, this is often more of a transient problem.
• Remove Tape & Labels: You must ensure that all plastic tape, shipping labels, and any glossy, strongly inked areas from cardboard are removed since these may not degrade well or could leach unwanted chemicals.

Best For:

• When building a new raised bed straight on a lawn or weedy area, efficiently suppresses current grass and weeds.
• Weed control in the short to medium term.
• Strengthening the soil under the bed as it breaks down.
• A major factor in lasagna or no-dig gardening techniques.

Hot Tip: Use basic brown corrugated cardboard; if at all feasible, avoid those with waxy coatings or heavy colored writing. To stop any stubborn weeds from finding a gap to sneak through, overlap the sections by at least 6-8 inches when laying it down. Wetting the cardboard completely after placing it helps it remain in place and begins the disintegration process.

Weed Barrier / Landscape Fabric: The Synthetic Choice for Weed Control

Gardeners that value long-term weed control often turn to this.

Advantages:

• Durable and Long-Lasting (for Weeds): Good quality landscaping fabric can offer weed suppression for many years.
• Water and Air Permeable: Selecting a top quality woven or spun-bond (non-woven) landscape fabric that expressly specifies it lets water and air pass through is really vital. This is necessary for strong plant roots and good soil.
• Relatively Easy to Install: Usually simple to size cut and lay down.

Drawbacks:

• Not Biodegradable (Usually Plastic): Most landscape fabrics are made of plastic—polypropylene or polyester—and will not decompose in the soil. Over time, they may begin to break down and release microplastics into your garden surroundings.
• Determined Weeds Can Still Be a Problem: Although it stops many weeds, more aggressive perennial weeds with sharp rhizomes (like some kinds of running grasses or bindweed) might eventually find their way through minor tears, around the edges, or even grow right through some thinner fabrics over time. Any soil or mulch that builds on top of the fabric might also sprout weeds.
• No Pest Protection: Landscape fabric provides no protection against gophers, voles, or moles.
• Can Impede Earthworm Movement: Though this is less of a concern with more permeable varieties, a very dense fabric could impede earthworm movement between the raised bed soil and the ground below.

Ideal For:

• Especially in ornamental beds or paths under a layer of mulch, long-term weed suppression.
• If your main objective is maximal weed control from below and you are okay with utilizing synthetic materials in your food garden, this can be applied in vegetable raised beds.

Important Warning: Make sure your garden use calls for a permeable landscape fabric. Solid plastic sheeting—like painter’s tarps or thick black plastic—will fully obstruct drainage and airflow, hence causing soggy, unhealthy soil.

Hardware Cloth / Wire Mesh (The Critter Stopper – Essential for Pest Areas!)

Should burrowing creatures be an issue in your area of the United States, this is usually the most dependable and best fix.

Advantages:

• Its superpower? The Absolute Best Defense Against Burrowing Pests! Correctly fitted hardware cloth offers an almost impenetrable barrier against gophers, voles, moles, and occasionally even rats or rabbits attempting to burrow in from underneath.
• Durable and Long-Lasting: Galvanized hardware cloth is quite rust-resistant and can survive for many, many years at the bottom of your raised bed.
• Allows Drainage & Root Growth: The mesh holes let water drain easily and plant roots (and earthworms) pass through into the soil below should they want.

Drawbacks

• Can Be More Expensive: Usually more expensive than cardboard or simple landscape fabric, hardware cloth is.
• More Labor-Intensive to Install: Installing more laboriously: Cutting heavy-gauge wire mesh to size and properly fastening it can be a bit more effort. Tools include wire snips, a staple gun or screws, and strong gloves are needed since the cut edges are sharp.
• Doesn’t Suppress Weeds: The holes in the mesh are big enough for weeds to grow through, hence if weed control is also a goal, you could think about putting cardboard behind the hardware cloth.

Ideal For:

• Gardeners in regions with documented ongoing gopher, vole, or mole issues. In many areas of the United States where these pests are prevalent, hardware cloth is seen as a necessary feature of raised bed building for food gardens.

For the greatest balance of pest prevention and longevity, use 1/4-inch or 1/2-inch galvanized hardware cloth. Make sure the components are cut large enough to not only cover the whole bottom of your raised bed frame but also to extend up the interior edges of the bed frame by a few inches (see the Pro Tip later!). Use strong-duty staples or screws to fasten it tightly to the frame, hence avoiding any openings for insects to enter.

Gravel or Stones (Usually Not Recommended! The Drainage Debate)

Some recommendations on adding a layer of gravel or stones at the bottom of elevated beds for drainage could reach you. For most cases, though, this is old advice and may even be harmful.

Advantages:

• It seems to let water run off the very bottom layer.

Drawbacks:

• Often NOT Recommended Directly Under the Soil in a Raised Bed: This is the main issue. Actually, putting a layer of coarse material—like gravel—under a finer grained material—like your soil mix—can produce a perched water table. The difference in texture prevents water’s downward migration, so it can become “stuck” in the soil just above the gravel layer, causing damp conditions exactly where your plant roots are located—the contrary of what you desire!
• Uses Up Precious Rooting Space: That layer of gravel is space your plant roots could otherwise be utilizing.
• Difficult to Remove: Removing a layer of gravel mixed with soil is somewhat inconvenient should you ever choose to alter your bed or dig deeper.
• No Weed or Pest Protection: Stops Pests and Weeds Not at All.

Best For (Very Particular, Restricted Situations):

• A gravel layer might be thought of, maybe, if your raised bed is going on an absolutely impermeable surface like solid concrete or asphalt and you have to build a void beneath the soil for excess water to gather and then drain away (e.g., via weep holes drilled in the side of the bed frame at the very bottom). Even so, you’d usually cover the gravel with a layer of permeable landscape fabric to prevent your soil from washing down into it.

Important Clarification: Good drainage in a raised bed comes from having a well-structured, porous soil mix across the whole depth of the bed, and ensuring the bed itself can drain out the bottom (if it’s on permeable ground) or through drainage holes (if it’s on an impermeable surface). Gravel at the bottom doesn’t suddenly produce adequate drainage in bad soil above it.

Natural Materials: Leaves, Branches, Twigs (A Hugelkultur-Lite Base)

Often referred to as “Hugelkultur-lite,” this technique can be quite effective for filling the bottom of extremely deep raised beds.

Advantages:

• Great for Deep Beds: Using large organic materials at the bottom can help you much on the amount of bought soil you must fill your raised bed if it is really deep—say, 18 inches or more.
• Recycles Garden ‘Waste’: Fallen branches, twigs, prunings, leaves, and other woody debris from your yard make excellent recycling material.
• Improves Soil Over Time: Over time, natural materials enrich soil by releasing nutrients back into the ground as they decay slowly over many years, therefore enhancing soil structure by generating air pockets and helping to retain moisture like a sponge.
• Mimics Natural Forest Floor Processes: It’s a very sustainable and nature-mimicking strategy.

Drawbacks:

• Slow Decomposition: Decomposing completely takes time; this is a long-term process.
• Potential Nitrogen Tie-Up (Initially): Using a very large amount of fresh, carbon-rich woody material—like fresh wood chips or lots of branches—without balancing it with nitrogen-rich “green” materials—like grass clippings, kitchen scraps, or manure—can cause some initial nitrogen depletion as the decomposing microbes work and temporarily tie up some nitrogen from the soil above. If the woody layer is deep down and you have lots of good soil on top, this is usually less of a concern.
• Not a Weed or Pest Barrier: This approach provides no defense against tunneling insects or weeds sprouting from underneath.

Most Suitable For:

• Generally, deeper raised beds—18 inches or deeper—are best for this.
• Gardeners curious about Hugelkultur ideas, permaculture, or those just searching for a sustainable approach to lower the amount of bought soil required to fill a somewhat deep bed.

Usually, you’d stack coarser woody debris at the bottom, then smaller twigs and leaves, then maybe some unfinished compost, and ultimately your good topsoil/compost blend.

4.6 Not anything! The Easiest Option—Usually Quite Acceptable!

Occasionally, the simplest answer is the best one.

Advantages:

• Simplest and most affordable choice: No additional installation effort, no supplies to purchase!
• Lets Plant Roots Reach into Native Soil: Should the soil under your raised bed be fairly good, letting your plant roots finally go down into it will provide them access to more nutrients, moisture (particularly during dry times), and a more stable environment.
• Encourages Earthworm Activity and Soil Life: It makes a smooth link between the soil in your raised bed and the ground soil below, so allowing beneficial earthworms and bacteria to move easily, which is fantastic for soil health.
• Excellent Drainage (If Native Soil Drains Well): Having no barrier guarantees that extra water from your raised bed can also drain away freely if the ground beneath your bed drains effectively.

Drawbacks:

• Offers No Protection Against Aggressive Weeds From Below: Persistent perennial weeds in the underlying soil will most likely grow up into your raised bed.
• No Protection Against Burrowing Pests: From below, gophers, voles, and moles will have easy access.

Ideal For:

• Generally, 12 inches or more is advised for deep raised beds if going liner-free for weed control from below. The deeper soil volume provides your plants lots of room before their roots could meet beneath weeds.
• When your raised bed is being placed on existing garden soil that is already fairly healthy, well-draining, and largely devoid of aggressive perennial weeds or known burrowing pest issues.
• When one of your objectives is to progressively enhance the soil under your raised bed over time by leaching nutrients and organic matter from the bed above.

Clearly, there are several choices, each with its own trade-offs.

What NOT to Put on the Bottom of Your Raised Garden Bed (Avoid These!)

Knowing what materials you should absolutely avoid using at the bottom of your raised garden beds is just as crucial as knowing what to possibly use. Some materials can be useless at best and outright hazardous to your soil and plants at worst.

Avoid these:

• Solid, Non-Permeable Plastic Sheeting: Avoid these: Solid plastic will totally prevent draining. Water will pool at the base of your bed, therefore producing a damp, waterlogged disaster that will kill plant roots and cause root rot. It also stops any good interaction with the soil underneath.
• Old Pressure-Treated Wood (Especially Pre-2003): Older pressure-treated wood usually contains chromated copper arsenate (CCA), which contains arsenic, a hazardous heavy metal. You certainly don’t want this seeping into the soil where you intend to cultivate food. Although newly treated timber utilizes less hazardous chemicals, it’s still usually best practice to only use untreated wood in or directly under your garden beds if there’s any possibility of contact with your soil.
• Old Carpets or Carpet Remnants: Especially synthetic carpets can include a mix of dyes, adhesives, synthetic fibres (which don’t decompose and can turn microplastics), stain repellents, and other chemicals you don’t want anywhere near your food plants. They could potentially trap unwanted moisture or block drainage.
• Large Rocks That Hinder Drainage (If Not Part of a Very Specific Drainage Plan): As we covered in the gravel section, simply throwing a layer of large, impermeable rocks at the bottom of a bed placed on soil can actually create drainage problems (the perched water table effect) rather than solve them.
• Anything That Could Leach Toxins or Unwanted Substances: This covers manufactured items like asphalt shingles, old tires, or any other such material whose composition you are uncertain about. Your garden soil, particularly if you are growing food, follows a rule: when in doubt, leave it out!

Use only items that have been shown to be safe and good for garden settings.

Fast Installation Instructions for Your Selected Bottom Layer

Once you have carefully selected the best material—or no material—for the bottom of your elevated garden bed, below is a rough guide on how to install many of the usual advised liners:

1. First, clear and level the area.
   • Clear the area where your raised bed will sit of any current large stones, sticks, or trash.
   • Should you intend to employ a smothering layer like cardboard, either remove any current grass or weed entirely (e.g., by digging it out or using a sod cutter) or mow it as short as feasible.
   • Make sure the ground where the bed frame will sit is fairly level. This will enable more even water distribution and increase the stability of your bed.
2. Putting in Cardboard or Newspaper:
   • Place your newspaper or cardboard in overlapping layers. For cardboard, 1-2 layers of corrugated cardboard is usually enough; for newspaper, at least 2-3 sheets thick.
   • At least 6-8 inches should separate the borders of every component. This is essential to stop weeds from locating any tiny openings to grow through.
   • Once set, use a hose to thoroughly wet the cardboard or newspaper down. This starts the breakdown process, helps it stay in place, and conforms to the ground.
3. Putting in Landscape Fabric:
   • Unroll your landscape fabric and trim it to roughly the size of your raised bed. Cutting it somewhat bigger than the precise footprint lets you raise it up the inside margins of the bed frame by a few inches if you choose, therefore helping to stop soil from leaking out the bottom edges of the frame and so producing a more orderly appearance.
   • Put it in position. You may wish to use landscape staples—also known as sod staples—to temporarily pin it to the ground if the cloth is quite lightweight or if it’s a windy day until you set your frame and soil on top.
4. Putting in Wire Mesh / Hardware Cloth:
   • Though it calls for additional work, this is rather important for pest control.
   • Measure and cut your hardware cloth precisely to fit the base of your elevated bed frame. Importantly, cut it big enough to allow edge bending upward to reach at least 4-6 inches up the interior walls of your frame; this is the “Gopher Overlap” from our Pro Tip!.
   • Working with hardware cloth calls for always wearing heavy-duty gloves since the cut edges are quite sharp. It’s also a smart idea to wear eye protection.
   • Put the mesh inside your constructed frame or put it down and construct the frame on top of it; then, fold the edges up inside.
   • Using a heavy-duty staple gun (with stainless steel staples if feasible, for durability), or by using screws with broad washers, firmly fasten the mesh to the interior of the frame. Make sure there are no holes for insects to squeeze through.
5. Put Your Raised Bed Frame:
   • Once your selected liner is in place (if you’re using one that goes under the frame, such cardboard or landscape fabric spread on the ground), carefully arrange your raised bed frame over it.
   • Should your frame be assembled and in its final location, you will attach a liner such as hardware cloth that fits inside the frame.

Your foundation ready, you are set for the next thrilling stage!

Layering for Success Above Your Chosen Base: Filling Your Bed

Now that the bottom layer is skillfully selected and in place (or, if you decided to go liner-free, the ground is carefully prepped), you are ready for the fun stuff: filling your raised bed with a fantastic soil mix your plants will love!

Although the details of making the ideal raised bed soil mix are a subject for another thorough tutorial, it’s worth noting quickly that just like the foundation, what you fill it with matters quite a bit. Sometimes called “lasagna gardening” or using “Hugelkultur” ideas for extremely deep beds, a layered approach can often be helpful. This could call for:

• A base layer of coarser organic materials would be twigs, small branches, if you chose the “natural materials” choice for the bottom.
• Your bulk fill then is usually a high-quality combination of topsoil, compost, and maybe other additives like coco coir or perlite for optimal drainage and aeration.
• For planting seeds or early seedlings, you might end with a finer layer of potting mix or compost at the very top.

If not more so, the quality of your soil mix is as crucial as the basis you place under it. They work together to provide the ideal conditions for your plants to send down roots and flourish!

Pro Tip: The “Gopher Overlap” for Ultimate Critter Defense!

Should you be placing hardware cloth to discourage tenacious burrowing insects like gophers or voles, which pose a genuine difficulty for many US gardeners, you want to make absolutely sure you’re doing it in the most efficient manner possible. Here is a vital advice:

Pro Tip: The ‘Gopher Overlap’ for Ultimate Critter Defense!

Don’t just lay hardware cloth flat on the ground under your raised flower bed and call it a day; install it at the bottom. You must build a constant, impenetrable barrier for the most strong and dependable defense against smart burrowing pests.

Cut your hardware cloth large enough to bring the edges of the mesh up the inside walls of your elevated bed frame by at least 4 to 6 inches. From the inside, then, firmly staple or screw this overlapping mesh straight to the wood (or other material) of your frame. Ensure your screws have washers to keep the mesh tight or your staples are close together.

Gophers or voles could otherwise attempt to squeeze or dig their way in between the frame and the mesh at the critical bottom edges, hence this “overlap” approach produces a complete, sealed “basket” of wire mesh with no gaps. Though it’s a bit more effort during installation, for gardeners in gopher-prone regions of the US, this careful ‘overlap’ approach is definitely worth its weight in rescued veggies and peace of mind!

Conclusion: The Correct Foundation Counts! Building Your Raised Bed From the Ground Up

Deciding what goes on the bottom of a raised garden bed is really a first step in preparing yourself for a successful, fruitful, and pleasant gardening experience for many years. The “correct” response differs for every gardener and every garden as we have investigated. Whether you’re mostly fighting persistent weeds that want to invade from below, fending off tenacious burrowing pests that see your plant roots as a buffet, or just starting fresh on new ground and want to give your plants the best possible environment, it really depends on your particular needs and goals.

You may build the ideal basis that will enable your plants to really flourish by carefully evaluating your goals, your garden site, and the various benefits and drawbacks of materials such as eco-friendly cardboard, robust landscape fabric, or critter-stopping hardware cloth (or even sensibly selecting no liner at all!).

You now have the information to choose the greatest, most educated choice for your US garden. Prepare to construct that bed confidently, fill it with great soil, and see your plants grow from the ground up!

Enjoy raised bed gardening!