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.
So forget those 5-gallon buckets for your indeterminate tomato vines—you want them in half-barrel planters (at least 15 gallons) or larger for a good harvest.
Just like the saying goes—Feed the soil, not the plants—you want to focus on building strong roots, not just healthy stems and leaves.
Roots that grow deep down in the soil are better able to anchor plants in the ground, maximize their water uptake, and pull in more nutrients and trace minerals.
If you’re getting a garden bed ready for planting, knowing the root depth of the plants you want to grow can help you determine how extensively to prepare the soil.