Creating a raised garden bed is a fantastic way to grow vegetables, herbs, and flowers with better soil control and drainage. However, many gardeners wonder, “What do I put under my raised garden bed?” The materials you choose beneath your raised bed can significantly impact soil health, drainage, weed control, and pest management. In this comprehensive guide, we’ll explore the best options to place under your raised garden bed, why they matter, and how to prepare the area for optimal plant growth.
Why Is It Important to Choose the Right Base for Your Raised Garden Bed?
The base layer under your raised garden bed serves several crucial functions:
- Weed Barrier: Prevents weeds from growing up into your bed.
- Drainage: Ensures excess water drains properly to avoid waterlogging.
- Pest Control: Reduces the likelihood of pests like burrowing rodents.
- Soil Health: Helps maintain the right environment for roots to thrive.
Choosing the wrong base can lead to poor drainage, invasive weeds, and soil compaction, all of which stunt plant growth and reduce yield.
What Are the Best Materials to Put Under Raised Garden Beds?
1. Grass or Sod
- Pros: Easy to place the bed directly on your lawn.
- Cons: Grass can grow up into the raised bed, competing with your plants.
Tip: If placing the bed on grass, remove the sod first or cover it with a weed barrier to prevent grass roots from invading.
2. Weed Barrier Fabric or Landscape Fabric
- What it is: A permeable fabric designed to block weeds while allowing water to pass through.
Benefits:
– Prevents weed growth without blocking drainage.
– Allows water and air to reach the soil.
– Durable and reusable.
How to use:
– Lay the fabric flat on the ground.
– Secure edges with garden staples.
– Place your raised bed frame on top.
Expert Insight: Landscape fabric strikes a perfect balance between weed control and drainage, making it a favorite among experienced gardeners.
3. Cardboard or Newspaper
- What it is: Layers of cardboard or newspaper act as a biodegradable weed barrier.
Benefits:
– Suppresses weeds effectively.
– Decomposes over time, enriching the soil.
– Inexpensive and eco-friendly.
How to use:
– Remove any tape or glossy materials.
– Lay down a thick layer (3-6 sheets) of wet cardboard or newspaper.
– Overlap edges to prevent weed gaps.
– Place the raised bed frame on top.
Note: This method works well when building beds directly on soil or grass.
4. Gravel or Small Rocks
- Purpose: Improves drainage and deters burrowing pests.
Benefits:
– Prevents waterlogging by allowing water to flow through.
– Creates a physical barrier against rodents like voles and moles.
How to use:
– Lay a 2-3 inch layer of gravel at the bottom of the bed (usually when building raised beds without a solid bottom).
– Combine with weed barrier fabric below the gravel for best results.
When to use: Ideal for heavy clay soils or areas prone to poor drainage.
5. Plastic Sheeting or Pond Liner
- Use caution: Plastic prevents water from draining properly and can cause root rot.
Best practice:
– Avoid placing plastic directly under the raised bed unless you want to block invasive roots or create a barrier over contaminated soil.
– If used, ensure adequate drainage holes are made.
6. No Material (Direct to Soil)
Some gardeners simply place raised beds directly on the soil.
Pros:
– Easy setup.
– Roots can expand into native soil, providing access to nutrients.
Cons:
– Weeds may grow up through the bottom.
– Soil compaction and poor drainage in some areas.
– Potential for pests.
Recommendation: If you choose this, thoroughly loosen the soil beneath and consider layering with cardboard or weed fabric for better results.
Step-by-Step Guide: Preparing the Ground Under Your Raised Garden Bed
Clear the Area
Remove grass, weeds, rocks, and debris from the bed’s footprint.Level the Ground
Use a rake to create a flat, even surface for your bed.Lay a Weed Barrier
Choose between landscape fabric, cardboard, or newspaper layers. Overlap the edges.Add Gravel (Optional)
For heavy or poorly draining soils, spread a 2-3 inch gravel layer.Place the Raised Bed Frame
Set your raised bed frame firmly on the prepared base.Fill with Quality Soil Mix
Use a blend of compost, topsoil, and organic matter tailored for raised beds.
Expert Tips to Maximize Raised Bed Success
- Avoid Using Plastic Underneath: It traps water and limits drainage.
- Consider Pest-Proof Mesh: Place hardware cloth under beds to deter voles and gophers.
- Ensure Proper Drainage: Raised beds with compacted soil underneath can cause root rot.
- Use Organic Mulches: Mulch your raised bed surface to retain moisture and suppress weeds.
- Test Soil pH: Raised beds can dry out faster; balance soil pH for healthier plants.
Frequently Asked Questions (FAQs)
Can I put a raised garden bed directly on the grass?
Yes, but it’s best to remove the grass or lay down a weed barrier like cardboard or landscape fabric to prevent grass from growing into your bed.
What’s the best weed barrier for raised beds?
Landscape fabric is durable and allows water drainage, but cardboard and newspaper are excellent organic alternatives that enrich the soil as they decompose.
Should I put gravel under my raised bed?
If your garden soil drains poorly or you want to deter pests, a layer of gravel can improve drainage and provide a pest barrier.
Is it okay to place a raised bed on concrete?
Yes, but you must use a raised bed with adequate drainage holes and fill it with quality soil. Consider adding a layer of gravel inside for better drainage.
Conclusion
Choosing what to put under your raised garden bed is a foundational step that affects weed control, drainage, and overall plant health. Using landscape fabric or biodegradable layers like cardboard provides excellent weed suppression while allowing water to flow freely. For areas with drainage issues or pests, adding gravel or mesh underneath can offer additional protection. Avoid plastic barriers that trap water and suffocate roots.
By preparing the ground thoughtfully, you create the ideal environment for your raised bed to thrive, leading to healthier plants and bountiful harvests. Ready to build your raised garden bed? Start with a solid base, and watch your garden flourish!
Take Action: Before placing your raised bed, spend time preparing the base using these proven methods. Your future self—and your plants—will thank you!
