Soil is the foundation of any container garden. It’s essential for establishing strong roots and enabling growth. But how deep should the soil be?
The answer varies depending on the size and shape of the container, as well as the type of plant you want to grow. Generally, a depth of several inches deeper than the root ball works best.
Especially for larger pots, a minimum depth of six inches is recommended so that plants have enough space to spread their roots and stabilize their growth. However, shallow-rooted plants or low-growing ones may not require as much depth.
For smaller pots or planter boxes, the depth should be adjusted accordingly—approximately two to three inches deeper than the root ball should do it. When planting in soil that has been amended with compost or fertilizer, take this into account; often, extra height is necessary if using amended soils.
You also must consider drainage when deciding how deep to go—it’s important for preventing waterlogging and pests from entering your container garden. Depending on your chosen plants’ needs, it might be beneficial to use a mix of potting soil with some sandy loam mixed in (approximately one part sand per four parts soil) for optimal drainage.
The bottom line: understanding each plant’s unique preferences comes first when deciding on the right soil depth for your container garden.