Companion Planting Chart

Companion planting is rooted in centuries of gardening tradition and increasingly supported by modern agricultural science. The mechanisms behind successful plant pairings include allelopathy, where certain plants release chemical compounds from their roots or foliage that suppress weeds or repel insects. Marigolds, for example, release alpha-terthienyl from their roots, which suppresses root-knot nematodes in the surrounding soil.

Trap cropping is another powerful technique: nasturtiums planted near squash attract aphids away from the main crop, sacrificing themselves to protect your harvest. Meanwhile, nitrogen fixation by legumes like peas and beans converts atmospheric nitrogen into plant-available forms in the soil, directly benefiting heavy-feeding neighbors like corn, tomatoes, and squash.

Physical relationships matter too. Tall plants like sunflowers and corn can provide natural shade for heat-sensitive crops like lettuce and spinach, while low-growing ground covers suppress weeds and retain soil moisture. The classic "Three Sisters" planting of corn, beans, and squash demonstrates multiple companion mechanisms working together in a single planting bed.