Marigolds repel most garden pests and protect the whole garden.
Contested
Marigolds don't repel pests in general. Their one real effect is narrow: a dense planting of the right Tagetes, grown before a crop, suppresses root-knot nematodes in the soil (not a scent that wards off flying insects). Enjoy them for colour and pollinators; use the nematode trick on purpose if you need it.
What is actually known
Marigolds have one real, narrow effect: some Tagetes suppress root-knot nematodes in the soil when grown as a dense preceding stand, via the root compound alpha-terthienyl — a soil biofumigant effect on a specific soilborne pest, handled as a role in this corpus, not a scent that wards off insects. The broad folk claim — that a few marigolds dotted among the vegetables repel aphids, whiteflies, cabbage moths, or rabbits by smell — has no reliable field support.
Evidence: not yet confirmed against its 1 source.
what this rests on - one pointer
University of Florida IFAS Extension, ENY-056 'Marigolds (Tagetes spp.) for Nematode Management' (read 2026-07-14): the effect is a dense preceding cover crop, not a scent repellent — 'alpha-terthienyl inhibits the hatching of nematode eggs'; 'Planting should be dense to ensure the best nematode control'; 'Marigolds cannot eradicate nematodes.' Backs the narrow root-knot-nematode mechanism; the general pest-repellent claim is unsupported.
When would that grow at your place? →
Cite this page
Milpa Gardens. "Marigolds repel most garden pests and protect the whole garden." Evidence grade: Contested. https://milpa.garden/beliefs/marigolds-marigold-pest-repellent/
A garden-planning corpus: every claim states its evidence grade and links its sources on the page. Cite it with the grade, and add the date you read it.