A raised garden bed should be from 2 to 3 feet above the surrounding soil and no wider than 4 feet. Add the soil ingredients in layers and mix and water at regular intervals as you fill the beds. If your soil contains too much clay, add some builders sand to it. If your garden soil is good, and you have enough of it, just use that. The soil option fills the raised bed with soil that is very similar to what you have in the garden. It’s organic, provides excellent drainage, and is specially blended for raised bed gardening. A major advantage of raised beds is that you are not stuck with the soil in the ground. Potting mix is too light for use in raised beds, while garden soil is too heavy. Plant health, moisture retention and proper drainage are all achieved with raised beds and also when you choose the right ingredients to fill your raised-bed garden. Raised Box Bed Build a raised box garden bed if your soil is heavy or drains poorly. Raised beds also need to be filled with soil, which can become expensive and requires a good understanding of soils and soil amending. Amending Basic Raised Garden Bed Soil. Elevated raised beds are even more expensive and require some degree of engineering to support the weight of the soil. Read more about raised bed soil combinations here. Whether deep or shallow, raised beds give a gardener a way to create ideal soil conditions on an even larger scale. One way to build this mix is to start with a raised bed soil mix that is half topsoil and half organic compost. Because Jill chose to build fairly tall beds, she used fill dirt for the bottom half of the beds. For the top half, she used some of her native soil and mixed it with well composted manure. Raised beds are more permanent than in-ground gardens, so planning for future use is essential. You can start from scratch and build a soil type for raised beds that works in your region for the plants you intend to grow. Tall beds means more soil. There is no need to buy anything. The “just right” solution is Miracle-Gro® Raised Bed Soil, a pre-mixed blend of the two.