Journal/Vegetable Garden · 6 min
Companion Planting: What Actually Works
Which vegetable companions have real evidence behind them, which are folklore, and a simple planting plan you can copy.
Quick answer
The most reliable companions are basil with tomatoes (repels whitefly), carrots with alliums (masks scent from carrot fly), and any flowering herb near fruiting crops (draws pollinators). Most other pairings are folklore.
Companion planting sits somewhere between science and folklore. Some pairings — like alliums with carrots — have peer-reviewed backing. Others — like the famous 'three sisters' — work through physical structure rather than chemistry. Many popular claims have no evidence at all.
Companions that reliably work
- Carrots + spring onions or garlic: the allium scent confuses carrot fly.
- Tomatoes + basil: basil deters whitefly and thrives in the same conditions.
- Brassicas + dill or fennel (nearby, not among): attracts parasitic wasps that hunt caterpillars.
- Any crop + nasturtiums or calendula: draws hoverflies that eat aphids.
Combinations to avoid
- Alliums + beans/peas: alliums slow legume growth.
- Fennel + almost anything: fennel releases growth-inhibiting compounds.
- Two heavy feeders side by side (tomatoes + brassicas): they'll compete and both underperform.
Frequently asked questions
Does marigold really repel pests?
French marigold (Tagetes patula) has been shown to reduce root-knot nematodes when grown as a whole-bed cover crop. As a border plant its main role is pulling in pollinators, not repelling pests.
Do I need to memorise complex charts?
No. Cluster brassicas together, alliums together, legumes together, and rotate them each year. Add flowers throughout. That gets you 90% of the benefit.
What is the 'three sisters' method?
Corn, beans and squash grown together — corn provides structure for the beans, beans fix nitrogen, squash shades the soil. It works because of the physical arrangement, not chemical interaction.
Try it yourself
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