Container Garden Planner & Spacing Calculator

Roots grow downward in search of water and nutrients, and many vegetables (tomatoes, peppers, carrots, eggplant) develop a deep tap-root or extensive root mass. A pot can be wide but if it is shallow the roots hit the bottom, circle, and become root-bound — which limits nutrient uptake, dries the soil out faster and stunts the plant. Width influences how many plants fit; depth determines whether they grow at all.

Companion planting pairs species that benefit each other through pest deterrence, pollinator attraction, nutrient sharing or microclimate effects (e.g. taller plants shading shorter ones). Some pairings are well-supported by research — basil near tomatoes repels certain pests, beans fix nitrogen useful to leafy greens — while others are folklore. The general guidance reduces monoculture risk and tends to improve yield even when individual mechanisms are debated.

Aim for roughly 2–3 cm (about an inch) of empty space between the soil surface and the rim. This headspace catches water during deep watering so it can soak in instead of running off, and gives mulch room. Filling to the very top wastes water and washes soil out every time you irrigate.

Containers have a limited soil volume that heats up faster, holds less moisture, and is exposed to wind on multiple sides. Roots cannot reach deeper layers to find water as they would in the ground. Smaller pots in particular can dry out within a single hot day, which is why moisture-hungry crops like cherry tomatoes and cucumbers benefit from larger containers and self-watering reservoirs.

Recommended spacing is the distance between plants that lets each individual reach full mature size with adequate light, airflow and root volume. Minimum spacing is how close you can plant if you accept smaller individual yields — useful for cut-and-come-again leafy greens but harmful for fruiting crops. This calculator uses recommended spacing so the projected plant count reflects healthy, productive specimens.