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Reference

Companion planting matrix for vegetable gardens

Pick a crop and see what to plant near it, what to keep apart from it, and the actual research-backed reason. This matrix only includes pairings with documented mechanisms - we've cut the folklore. Sources: University of Maryland Extension, NC State Extension Gardener Handbook, and the Rodale Institute companion planting research summaries.

What companion planting actually does (and what it doesn't)

Most companion planting claims are not supported by controlled research. The classics that DO have evidence:

  • Three Sisters (corn + beans + squash): documented by multiple agronomy studies. Corn provides trellis, beans fix nitrogen for corn, squash leaves shade out weeds and discourage raccoons. Michigan State Extension.
  • Tall + short crop pairings: shading benefits the short crop (lettuce under tomato or corn extends harvest by 2-3 weeks in summer per UMN Extension).
  • Trap crops: nasturtium pulls aphids off brassicas in many studies. Blue Hubbard squash pulls cucumber beetles off main squash crop.
  • Allelopathy: black walnut produces juglone that kills tomatoes and many other plants within drip line. Fennel is allelopathic to many crops - keep it alone.

What is mostly folklore: basil "improving tomato flavor," marigolds "repelling all pests," chamomile being a universal "sick plant healer." These pairings won't hurt anything but don't expect miracles. The pairings in this tool are limited to the ones with documented mechanism, per Maryland and NC State Extension reviews.