What base layer works best under raised beds?
Written by
Tina Carter
Reviewed by
Prof. Martin Thorne, Ph.D.Choosing the appropriate base layer underneath your raised beds helps eliminate weeds, enhances drainage, and prevents burrowing animals. I figured this out after I lost my first garden to some gophers. A good layering system consists of combining a physical barrier layer with a proper drainage fill layer. The physical barrier will protect your plant's roots while providing your growing medium with the best possible conditions from the ground up.
Weed Suppression
- Cardboard sheets block existing weeds effectively
- Landscape fabric prevents new weed growth
- Newspaper layers decompose safely over time
- Avoid plastic sheeting that causes drainage issues
Pest Prevention
- Hardware cloth stops gophers and moles
- 1/4 inch mesh excludes most burrowing insects
- Extend barriers 12 inches beyond bed perimeter
- Overlap sections by 6 inches to prevent gaps
Drainage Solutions
- Coarse gravel layers improve water movement
- Sand prevents soil compaction in wet areas
- Perforated drainage pipes redirect excess water
- Slope beds slightly for natural runoff
For viewable effectiveness, install layers in the order described. I place hardware cloth directly on the soil first to block all access for the rodents. After laying the hardware cloth, I put a gravel layer approximately 2-3 inches thick for drainage. Last, the landscape fabric once again prevents soil from mixing, while allowing the water to pass through. This triple-layer protection will finally solve the battles I've had with the pesky gophers.
Consider your specific soil conditions when selecting materials to ensure optimal performance. For clay soils, you want thicker layers of gravel, about 4 inches, to allow for drainage. Sandy soils can benefit from more landscape fabric, particularly to hold onto some nutrients. For my own garden, which has heavy clay soil, I added perforated pipes underneath my gravel to avoid the soil becoming waterlogged in the rainy months.
There are affordable alternatives that work well. Cardboard from a shipping box makes a great short-term weed barrier, which I cover with grass clippings to promote quicker breakdown. Crushed rock from a construction site inevitably provides a free drainage layer when washed thoroughly. Always opt for function rather than aesthetics for buried base layers.
You need to maintain your base layers on an annual basis to guarantee a longer performance. I inspect hardware cloth every spring for signs of corrosion or damage. I usually replace landscape fabric every 3 to 5 years when roots penetrate it. I may go back and refresh gravel layers if the soil washes down over time. Doing this will avoid unexpected problems during peak growing seasons for your garden.
Avoid common beginner errors, such as using plastic sheeting, which can cause root rot. This certainly happened when tomato plants got flooded due to heavy rains. Use permeable materials that are effective in controlling weeds and allow for proper drainage. Having the right foundation for your gardening is crucial to your success and overall sustainability in gardening.
Read the full article: Best Raised Bed Materials for Your Garden
