Raised garden beds are a popular choice for gardeners, offering both aesthetic and functional benefits. They can be made of beautiful cuts of wood and provide natural drainage, while also allowing for better soil moisture and temperature control. However, when it comes to raised beds, soil depth is a crucial factor that can make or break your gardening success.
Soil depth requirements vary depending on what you are growing. Flowers may only need a few inches for their roots to spread, but vegetables require more room to thrive. The majority of a vegetable’s roots settle within the top 6 to 8 inches of soil, so it’s important to provide enough available nutrient-rich soil to sustain growth.
To ensure maximum utilization, a raised bed should be at least 8 inches in height. Anything less can stunt plant growth and produce unsatisfactory results. Well-designed raised beds are intentionally built to be 8 inches or taller for this root depth reason. When initially filling your raised garden bed with soil, it may look like you have filled it to the brim, but new soil will compress. Overfill your garden bed by about an inch or two, moisten the soil to allow it to settle, and add more if the level falls below the top of the garden bed.
If you need more soil depth, there are two options. The first is double-digging, which involves digging up to 2 shovel-blades deep into the ground where you plan to place your bed. Remove rocks and debris, and check for any roots that already occupy that space. Once cleared, pour the freshly aerated and sifted dirt back in, and set up your raised bed. This method is best if your raised bed is seated on the earth and not concrete. It allows vegetables to continue growing past the raised bed limitations if necessary.
The second option is stacking. Raised garden bed engineers created stackable raised garden beds so you can have a deeper planting environment without double-digging. Stackable raised garden beds are available in a variety of heights and styles, making it easy to choose the right option for your needs.
It’s important to note that not all vegetables require the same soil depth. Shallow-rooted vegetables can still grow deeper if necessary, but deep-rooted vegetables like carrots, sugar beets, turnips, and radishes require soil depth deeper than 8 inches. If you’re unsure of a plant’s root depth needs, a quick online search of the varietal you’re considering should yield an easy answer.
Roots will spread where available, which is why some vegetable roots will spread outward in shallow environments. However, this comes at the cost of planting space because, at the end of the day, plants are fighting for nutrition. To start off on the right foot, ensure your chosen garden bed is 8 inches or taller, and fill it all the way to the top so your plants have plenty of room to grow. Whether you opt for double-digging or stacking, providing the right soil depth is essential for a successful raised garden bed.