Companion planting: complete crop-by-crop guide
What to plant next to your tomatoes, broccoli, and peppers — and what to keep apart. Real research from Cornell, Penn State, and Texas A&M, not folk wisdom. Pick a crop below for the full friend / foe matrix.
Companion planting is one of the most over-claimed and under-researched topics in home gardening. The folk wisdom (marigolds repel everything, garlic protects roses) is mostly oversold. But there are real, replicable, Extension-research-backed companion effects worth knowing about: trap crops that pull pests away, allelopathy where one plant suppresses another, pollinator attractants that boost yield in nearby beds, and intercropping that maximizes bed productivity.
This hub is the master entry point. Pick your crop below for the full friend / foe matrix specific to it.
How we built these guides
Every crop-specific companion guide on Outdoor Plant Care follows the same structure:
- Friends with evidence — pairings backed by replicated Extension or peer-reviewed studies, with the source cited inline.
- Friends with tradition — pairings that show up everywhere in folk gardening but lack hard research. We list them, label them, and let you decide.
- Foes — combinations that demonstrably hurt yield (allelopathy, disease sharing, root competition, or shared pests).
- Practical layout — bed planning notes for actually putting it together.