The companion planting matrix shows which plants grow well together and which are incompatible. Search for a vegetable or herb to see its beneficial companions and plants to keep away.
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How to Use the Companion Planting Matrix
Companion planting leverages natural plant relationships to improve your garden without chemicals. Some companions repel pests, others attract beneficial insects, and some even improve the flavor of their neighbors.
The Three Sisters
The most famous companion planting combination is the Native American "Three Sisters": corn, beans, and squash. Corn provides a trellis for beans to climb. Beans fix nitrogen that corn and squash need. Squash's large leaves shade the ground, suppressing weeds and retaining moisture. Each plant benefits the others.
Pest Deterrence
Marigolds (Tagetes) are the workhorses of companion planting — they deter aphids, nematodes, and whiteflies. Plant them around tomatoes, peppers, and throughout the vegetable garden. Nasturtiums attract aphids away from vegetables (trap cropping). Basil repels thrips and mosquitoes near tomatoes and peppers.
Allelopathic Plants
Some plants release chemicals that inhibit nearby plants — a phenomenon called allelopathy. Fennel is the most notorious example: it harms most garden plants and should be isolated. Black walnut trees release juglone, which kills tomatoes. Even sunflowers can inhibit nearby potato plants. Understanding these relationships prevents mysterious crop failures.
FAQ
Is this companion planting matrix free?
Yes, completely free with no signup required. The companion planting data is based on widely researched horticultural relationships between common garden plants.
What is companion planting?
Companion planting is the practice of growing different plants near each other for mutual benefit. Benefits include pest deterrence (marigolds repel nematodes), nitrogen fixation (beans fix nitrogen that corn uses), physical support (beans climb corn stalks), and pollinator attraction. Some plant combinations are antagonistic — one plant inhibits the growth of the other.
Do tomatoes grow well with basil?
Yes — tomatoes and basil are one of the most well-known companion pairs. Basil is believed to repel thrips, aphids, and whiteflies from tomatoes, and some gardeners report improved tomato flavor when basil grows nearby. They also have similar growing requirements (full sun, regular water) making them easy to care for together.
What should I not plant near peppers?
Avoid planting peppers near fennel (stunts most plants), brassicas (broccoli, cabbage, kale — they compete), and apricot trees. Peppers do well with basil, carrots, tomatoes, and marigolds. They also do fine near other nightshades (tomatoes, eggplant) since they share the same pests and growing conditions.
Why is fennel bad for the garden?
Fennel is allelopathic — it releases chemicals that inhibit the growth of most nearby plants. Keep fennel isolated in its own pot or a remote garden area. Almost every common vegetable (tomatoes, peppers, beans, brassicas) is negatively affected by fennel. The exception is dill, which is similarly allelopathic but less aggressive.