The Best Soil for Raised Garden Beds: A Complete Guide (2024)

FAQs

The Best Soil for Raised Garden Beds: A Complete Guide? ›

Soil taken from your yard or a garden bed is too dense to use in a pot or raised bed. Instead, for containers, you'll want to use potting mix (also called potting soil), a lightweight and fluffy alternative. For raised beds, you'll want to use a blend of potting mix and garden soil.

Fill the bed with compost and a soilless growing mix in a 1:1 ratio. Topsoil can be added (up to 20% by volume) for beds that are at least 16 inches deep.

Raised bed soil is nutrient rich and contains a higher percentage of organic material than garden soil. However, you should also add additional organic fertilizer throughout the growing season to ensure a productive harvest. Organic and natural fertilizers include compost, algae and worms.

Gardening magazine's trial of the best soil mixture for raised beds found that a blend of 50% topsoil, 25% coarse sand and 25% compost was best.

The soil is the key ingredient to a successful raised vegetable bed. Get enough light topsoil or raised bed soil to fill the estimated depth of the raised bed. Since tomatoes are heavy feeders and prefer a rich, organic soil, mix in two- to three-inch layers of compost or cow manure to the top one-third of the topsoil.

Raised beds that are small and shallow (under 12 inches deep) are typically only filled with soil. Adding other organic materials to shallow beds usually isn't a good idea. Sticks, twigs, and other materials further reduce the limited soil space and can interfere with plant root growth and water drainage.

We recommend buying high-quality, nutrient-rich soil in bulk. Or, you can make a soil mix with equal parts topsoil, organic materials (leaves, composted manure, ground bark), and coarse sand.

Whether deep or shallow, raised beds give a gardener a way to create ideal soil conditions on an even larger scale. While potting mix alone is too light for use in raised beds, creating a 50:50 blend of potting mix and Miracle-Gro® All Purpose Garden Soil will give just the right balance.

Raised Bed Soil: Where Garden Soil and Potting Soil Combine

You want to use far more garden soil than potting mix, around a 5:1 ratio. You can also make your own raised bed mix by mixing all the individual parts of garden soil and potting soil, so topsoil, bark or peat, compost, and perlite or vermiculite.

In general, with proper maintenance, the soil in a raised bed can last for many years. Here are some guidelines for how long raised bed soil can remain viable: Soil that is well-maintained and regularly amended with organic matter can last for up to 10 years or more.

What is the best soil enhancer for vegetable gardens? ›

Compost, manure, worm castings, leaf mold, and biochar are a few examples of animal and plant-based soil amendments that enrich the soil with organic matter. Azomite, dolomitic limestone, greensand, and gypsum are several mineral-based soil amendments that add essential nutrients to the soil.

Types of Soil for Vegetable Gardens

Loamy Soil: The gold standard for most gardeners, loamy soil has a balanced mix of sand, silt, and clay. It retains moisture while ensuring good drainage and is rich in nutrients and organic matter.

Avoid chalk topsoil as much as possible; look for loam instead. Loam is the best kind of soil to use because it's suitable for your plants and has a neutral pH balance that will not alter your vegetation's properties. To get the most out of your topsoil, consider screening it.

Compost and composted manure are great additions to the soil for tomatoes and lots of other plants. Compost adds basic nutrients and improves soil structure. Composted manure provides nutrients all season long. Composted manure: This provides a slow release of nutrients over the growing season.

The Best Height for Raised Beds

Keep in mind that beds 18 inches deep or more will have better drainage than shorter beds. While most plants don't need anything deeper than 18 inches, I prefer beds that are two feet deep (24 inches). The extra height is mostly just for the ease and convenience of the gardener.

Tomatoes should ideally be grown in a raised bed that's at least 15 to 18 inches deep. Many of my clients in Houston are successfully growing tomatoes in 12-inch deep raised garden beds, but their plants tend to be a little stunted compared to plants in deeper beds.

On its own, topsoil is not a great growing medium and I would recommend mixing in compost. Bulk Filling raised beds: Because it is often more cost-effective to purchase topsoil than garden or raised bed soil, bulk-filling new raised beds with a mixture that includes topsoil is a great way to get them started.

So if the soil in your garden is very shallow, or you are making new garden beds, adding or replacing a lawn, or putting in raised beds and need to add new soil, top soil is what you need.

For a 4x8-foot raised bed with a 6” height, using Mel's Mix: about 5 cubic feet each of compost, peat moss, and vermiculite is needed. It usually takes about two to three bags of purchased fertile mix (1.5 cubic feet each) to cover the bed surface to a depth of 2 inches.

Eventually, the plants will take all the nutrients from the soil—there is not an endless supply, even if you start with the best soil. That means you need to be adding compost into the mix frequently. Before planting something new, add a 1- to 2-inch layer of fresh compost to renew the nutrient base for your plants.