Companion planting chart for vegetable crops
Companion planting is the oldest form of pest control available to a smallholder: it costs nothing but planning. This chart lists pairings that repeatedly hold up in the field, the reason each works, and the combinations that quietly cut your yield.
How companion planting actually suppresses pests
Three mechanisms do most of the work. Aromatic plants mask the volatile compounds a pest uses to find its host. Flowering strips feed the parasitic wasps and ladybirds that eat aphids and caterpillars. And deep-rooted plants next to shallow-rooted ones stop the two competing for the same water.
None of this replaces scouting. Companion planting lowers pest pressure; it does not make a field immune. Walk your rows twice a week and photograph anything unusual.
Laying out the rows
Alternate rows work better than perimeter borders for aromatic repellents, because the scent has to sit inside the canopy where the pest is searching. Keep flowering insectary strips on the field edge instead — beneficial insects travel, pests mostly do not.
- Marigold every fourth row inside tomato and brinjal blocks, not just as a border.
- One row of onion or garlic between every three rows of leafy greens.
- A 1 m flowering strip (coriander, dill, sunflower) along the windward edge.
- Never intercrop two plants from the same family — they share the same diseases.
Reading the chart with your own field in mind
Spacing, soil and local pest species change the result. Treat the chart as a starting hypothesis, test it on two beds first, and keep the pairing only if the pest count on the test beds is visibly lower after one full cycle.
Companion and antagonist pairings by crop
| Crop | Plant with | Why it works | Keep away from |
|---|---|---|---|
| Tomato | Marigold, basil, garlic | Marigold roots suppress root-knot nematode; basil masks whitefly cues | Potato, brinjal (shared blight) |
| Chilli | Coriander, onion | Coriander flowers feed aphid predators | Fennel |
| Brinjal | Marigold, cowpea | Cowpea fixes nitrogen and pulls shoot borer away | Tomato, potato |
| Okra | Sunflower trap rows, basil | Sunflower intercepts cotton bollworm egg-laying | Dense maize shade |
| Onion / garlic | Carrot, lettuce, brassicas | Sulphur volatiles deter carrot fly and cabbage moth | Peas, beans |
| Maize | Cowpea, pumpkin | Classic three-layer system: nitrogen, shade, ground cover | Other tall cereals |
| Cabbage | Dill, onion, mint | Dill hosts parasitic wasps that attack cabbage caterpillars | Strawberry, tomato |
| Cucumber | Radish, nasturtium | Radish deters cucumber beetle; nasturtium is a trap crop | Aromatic herbs (sage) |
| Beans / pulses | Maize, cucumber, carrot | Nitrogen fixation feeds the heavy nitrogen users | Onion, garlic |
Frequently asked
Does companion planting replace pesticide?
No. It reduces pest pressure enough that organic sprays such as neem or a soap solution become sufficient in most seasons. In an outbreak year you will still need to intervene.
How much yield space does intercropping cost?
Typically 10-20% of the main-crop plant population, usually offset by the intercrop's own harvest and by lower spray costs.
Do marigolds work against all nematodes?
African and French marigold suppress root-knot nematode specifically, and only when grown for a full cycle in the same soil. A border planted late in the season does very little.
Not sure what you are looking at?
Photograph the leaf and PlantIQ diagnoses it on your device — no signal needed.