Check compatibility between plants like tomatoes, basil, and carrots.
Companion planting pairs garden vegetables, herbs, and flowers that thrive when grown side by side and separates pairs that compete or share pests. Our planner accepts up to ten crop choices and returns a compatibility grade plus a brief reason — handy for backyard beds in USDA zones 3–10 where the same square foot has to feed several families per season.
The tool evaluates each pair against a curated table drawn from extension-service literature (Cornell, Oregon State, Iowa State) covering classic combinations such as the Three Sisters (corn + pole bean + squash), nightshade neighbors (tomato + basil), and known antagonists (fennel near almost everything, brassicas near strawberries). Scores fold three factors: root-zone competition, shared pest pressure, and complementary nutrient demand (a heavy N feeder paired with a legume that fixes nitrogen on rhizobium nodules earns a positive flag).
Plant tomato, basil, and onion in the same 4×4 ft bed. The calculator marks tomato+basil as strongly compatible (basil repels thrips and the heavy water demand matches) and tomato+onion as neutral with mild pest synergy against aphids.
Enter corn, pole bean, and winter squash. Output shows the canonical Three Sisters positive grade: corn provides the bean trellis, bean supplies nitrogen, squash leaves shade the soil and discourage raccoons.
Pair fennel with tomato or beans — the planner returns a negative grade because fennel releases allelopathic compounds that stunt most Solanaceae and Fabaceae neighbours.
They aggregate companion-planting tables from cooperative-extension publications (Cornell, Iowa State, RHS Wisley) and peer-reviewed allelopathy reviews. Folk-lore-only pairings are excluded.
No. Companion planting is the same-season question. For next-season rotation, plan to follow a heavy feeder (corn, brassicas) with a legume to restore nitrogen.
Yes for pollinator and pest-deterrent flowers (marigold, nasturtium, borage, calendula). Strictly ornamental species without documented effects on neighbors are not scored.