What Not to Plant With Tomatoes

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GardenSays

Keep away from tomatoes: Potatoes, Corn, Cabbage, Broccoli, Kale, Fennel, Raspberry. Use caution with: Peppers, Eggplant, Strawberries, Mint, Rosemary, Sage, Lavender, Sunflower, Dill, Tomatillo, Jalapeno.

Keep apart: 7
Caution: 11
All flagged as: Possible conflict

Potatoes (possible conflict): The worst tomato neighbor: same species family, and both host early and late blight — spores move freely between them. Extension guidance is explicit about keeping them apart.

Typical estimate · 2 verified sources · Checked 2026-07-15 · How we decide

The link reopens this exact calculation.

Why

Corn (possible conflict): The corn earworm and the tomato fruitworm are the same insect (Helicoverpa zea) — planting them together concentrates its favorite two hosts, and tall corn shades tomatoes.

Cabbage (possible conflict): Brassicas and tomatoes are a long-standing 'keep apart' pairing: heavy feeders competing for the same nutrients, and tomatoes are traditionally said to inhibit brassica growth.

Broccoli (possible conflict): Same as cabbage — two heavy feeders with a traditional antagonism; neither does its best crowded by the other.

Kale (possible conflict): A brassica like cabbage and broccoli — the traditional advice to keep brassicas and tomatoes apart applies, though kale's smaller size makes it the least-bad of the family.

The strongest evidence tier covers trap crops, pollinator/predator attraction, and documented pest or disease suppression — most other 'good' pairings are really about avoiding competition, not a special boost.
Folklore-tier pairings (traditional scent/repellent claims) are marked as garden tradition, not established science — they're listed because they're harmless, not because they're proven.

When this doesn't apply

A healthy, well-spaced garden forgives most 'caution' pairings — disease history in that bed is what makes them matter.

How this was calculated

1. Exclusion rule18 plants
Pairs rated 'bad' (keep apart) or 'caution' out of 41 evaluated pairings.
2. Strong evidenceSource guidance
Mechanism is supported in extension or peer-reviewed research.
3. Practical compatibilityCalculated result
Not formally studied as a pairing, but the reasoning is a real, verifiable resource/timing/ecological fact (shade, root depth, season length, shared needs) — not a claimed pest-repelling magic.
4. Possible conflictCalculated result
A real, documented or strongly plausible reason to keep these apart or plant with care — shared disease, allelopathy, competition, or resource mismatch.
5. Folklore — insufficient evidenceGardenSays estimate
A long-standing companion-planting story (often a claimed scent/repellent effect) with no established scientific mechanism for this specific pairing. Treat as garden tradition, not proven fact.

Data sources

University of Minnesota Extension — Companion planting in home gardens — Some companion effects (trap crops, pollinator attraction, nematode suppression by marigolds) are documented; many traditional pairings lack formal evidence. (checked 2026-07-15)
University of Minnesota Extension — Growing tomatoes in home gardens — Avoid planting tomatoes near potatoes (shared blight) or where related crops grew the previous year. (checked 2026-07-15)

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