PlantAlong

What to plant with carrots

Sources list Onions, Lettuce, Tomatoes, Peas and Garlic as good companions for carrots. Keep carrots apart from Dill. Only 2 pairings have been tested in a study; the rest are guidance or tradition.

Pairings
7
Last reviewed
Photo: Markus Spiske / Pexels
Good neighbors first, then plants to keep apart. Each one says how strong the evidence is.

Helps

  • Onions Tested in a study

    Intercropped onions reduced carrot fly (Psila rosae) attack on carrots, probably because onion volatiles disrupt host finding; onion thrips on the onions were also reduced.123

    Conditions (Uvah & Coaker 1984, abstract only): effect greatest with young onions and higher onion:carrot plant density ratios, and virtually ineffective once onions began to bulb. Matters only where carrot fly is a pest. WSU EM128E separately advises pairing taproot carrots with shallow-rooted onions to limit root competition (guidance, no study cited for this pair).

  • Lettuce Extension guidance

    Deep-taprooted carrots paired with shallow, wide-rooted lettuce use different soil layers, so their roots compete less.23

    WSU EM128E recommends this root-depth pairing as practical guidance; no study of this pair is cited. The UC tradition chart lists each as the other's companion.

  • Tomatoes Traditional pairing3

  • Peas Traditional pairing3

  • Garlic Traditional pairing3

    The chart says "onion family"; garlic is an onion-family (Allium) crop. The carrot fly study tested onions, not garlic.

No clear effect

  • Marigold Tested in a study

    Claimed: French marigold protects carrots from carrot fly. Tested: mixing carrots with French marigold (Tagetes patula) did not reduce carrot fly.1

    Single field study (Uvah & Coaker 1984), abstract only read. The UC tradition chart does not list this pair.

Keep apart

  • Dill Traditional pairing3

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. Entomologia Experimentalis et Applicata 36(2):159-167 (John Wiley & Sons); abstract read via FAO AGRIS, Effect of mixed cropping on some insect pests of carrots and onions, 1984. Retrieved 2026-11-02.
  2. Washington State University Extension, Gardening with Companion Plants (Home Garden Series), EM128E, December 2023. Retrieved 2026-11-02.
  3. 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.