PlantAlong

What to plant with tomatoes

Sources list Marigold, Carrots, Onions, Garlic, Cucumbers and Nasturtium as good companions for tomatoes. Keep tomatoes apart from Potatoes and Fennel. Only 2 pairings have been tested in a study; the rest are guidance or tradition.

Pairings
9
Last reviewed
Photo: Thể Phạm / Pexels
Good neighbors first, then plants to keep apart. Each one says how strong the evidence is.

Helps

  • Marigold Tested in a study

    French marigold grown alongside tomato slowed glasshouse whitefly build-up (airborne limonene). Marigold grown before tomato reduced root-knot nematode galling in the following tomato crop.1234

    Whitefly: glasshouse trials with marigolds present all season; adding them after whitefly build-up gave minimal reduction (Conboy 2019). Nematodes: only as a cover crop planted at least 2 months before, on the same site, in soil above 15 °C, with a resistant cultivar (Ploeg & Maris 1999; UF/IFAS ENY-056). Interplanting for nematodes is "probably not" effective, and marigold increases some nematodes (ENY-056).

  • Carrots Traditional pairing4

  • Onions Traditional pairing4

    The chart says "onion family".

  • Garlic Traditional pairing4

    The chart says "onion family"; garlic is an onion-family (Allium) crop.

  • Cucumbers Traditional pairing4

  • Nasturtium Traditional pairing41

    In Conboy 2019 glasshouse trials a marigold mix that also held basil, nasturtium and Chinese cabbage reduced whitefly on tomato; nasturtium alone was not tested.

Disputed

  • Basil Tested in a study

    Claims: basil raises combined yield, improves tomato flavour and masks tomatoes from thrips and hornworms. Garden-scale trials found no consistent flavour effect and mixed yield results.56714

    Bomford 2004 thesis (not peer reviewed): basil companions gave a mean 20% relative-yield advantage, largest at high density and high basil share; no consistent taste preference. Bomford & Butler 2003 abstract: no LER significantly above 1; tomato pests did not respond. Penn State says basil masks tomatoes from thrips and hornworms but cites no study. Conboy 2019 (glasshouse): a marigold mix that included basil reduced whitefly; basil alone untested.

Keep apart

  • Potatoes Extension guidance

    Shared late blight: the pathogen overwinters mainly on infected potato tubers and spreads by wind to nearby tomatoes.84

    WSU HortSense advises against planting the two close together. The UC tradition chart also lists them as incompatible (without giving a reason); we did not find a field study of planting distance.

  • Fennel Traditional pairing4

Traditional pairings come from a UC Master Gardener chart that traces to the UC Davis Edible Landscaping Handbook and ATTRA. The chart gives no reasons, and we found no trial of these pairs; treat them as garden lore.

Sources

  1. PLOS ONE 14(3): e0213071, Companion planting with French marigolds protects tomato plants from glasshouse whiteflies through the emission of airborne limonene, March 1, 2019. Retrieved 2026-11-02.
  2. Journal of Nematology 31(4S):709-714 (Society of Nematologists); PMC2620405, Effect of Temperature on Suppression of Meloidogyne incognita by Tagetes Cultivars, December 1999. Retrieved 2026-11-02.
  3. University of Florida, IFAS Extension (Entomology and Nematology Department), Marigolds (Tagetes spp.) for Nematode Management (ENY-056), reviewed Reviewed November 2019; page footer "Reviewed: 01/2024". Retrieved 2026-11-02.
  4. University of California Agriculture and Natural Resources (UCCE Master Gardener Program), Companion Planting Chart: Companion planting in the vegetable garden, File dated 2023-09 in URL path; no date printed. Retrieved 2026-11-02.
  5. West Virginia University, Plant and Soil Science (Ph.D. thesis); record on Organic Eprints, Yield, pest density, and tomato flavor effects of companion planting in garden-scale studies incorporating tomato, basil, and Brussels sprout, 2004 (deposited 19 Dec 2005). Retrieved 2026-11-02.
  6. Meeting abstract (ASA-CSSA-SSSA 2003 annual meetings abstracts collection, mirrored by Prince of Songkla University library), Do Tomatoes Love Basil But Hate Brussels Sprouts? Evaluating Popular Companion Planting Claims in Garden-Scale Studies (NE_05-bomford156693-oral), 2003. Retrieved 2026-11-02.
  7. Penn State Extension, Herbs Make Good Plant Partners and Companions, Updated April 22, 2026. Retrieved 2026-11-02.
  8. Washington State University Extension (HortSense), Tomato: Late blight (HortSense fact sheet), reviewed Last review date: 2026-08-28. Retrieved 2026-11-02.