Root depth is a topic that isn’t often considered when we think about growing in containers, building raised beds, or planning an irrigation system for our garden.

But knowing how deep the roots of your plants reach is one of the most important pieces of the puzzle, especially if you’re working with limited space.

We tend to visualize our plants growing up or out, but before we transplant that first seedling, we need to know how deep they’ll go beneath the surface as well.

Why does root depth and soil depth matter?

Most plants will grow within the space you allow them. They’ll survive with a minimum of soil depth, but they’ll thrive if you give them as much room as possible for their roots to branch out and breathe.

For example, shallow-rooted plants like lettuce may do better in soil that’s high in clay and doesn’t drain well.

Knowing the root depth of vegetables can help you plan your garden better

Raised beds built over grass or dirt typically don’t need to be more than the standard 8 to 12 inches in height because the roots can sink into the subsoil.

Root depth can help determine the best height for raised garden beds

Hydrozoning is the practice of grouping plants with similar water needs together in order to conserve moisture and irrigate more efficiently.

Gardeners in dry climates can use root depth to help with hydrozoning

For example, a cucumber plant sends down a single tap root 3 to 4 feet deep. The majority of its roots, however, extend outward about 2 feet and are concentrated just below the soil surface.

It’s not just how deep, but how wide

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