Do Marigolds Actually Repel Garden Pests?
The Verdict: Mostly busted. Marigolds suppress root-knot nematodes when grown as a cover crop, but they do not repel most above-ground pests.
Why People Believe This
This one has been handed down for generations. Plant marigolds around your vegetables and the bugs will stay away. It sounds so simple and natural that it just feels true. The bright flowers, the pungent smell, the long tradition. There is a kernel of truth here, which is exactly what keeps the myth alive.
What the Research Says
UC ANR research confirms that French marigolds (Tagetes patula) produce alpha-terthienyl, a compound toxic to root-knot nematodes. But here is the catch: the marigolds need to be grown as a solid cover crop for at least two months before being tilled in, not just planted as a border. A few marigolds tucked between your tomatoes will not meaningfully reduce nematode populations.
As for above-ground pests, UC IPM has found no reliable evidence that marigold scent repels aphids, whiteflies, hornworms, or other common garden insects. Some studies even show that marigolds attract spider mites and slugs. In Santa Cruz County, where we deal with everything from aphids to earwigs, a ring of marigolds around your raised beds is not a pest management plan.
What to Do Instead
Enjoy marigolds for their beauty and pollinator value, but rely on proven integrated pest management (IPM) for actual pest control. Encourage beneficial insects by planting a diverse mix of flowering plants: sweet alyssum, yarrow, and California buckwheat all attract predatory insects that eat pests. For nematode problems in your soil, consider a dedicated summer cover crop of French marigolds tilled in before fall planting.
This week: Plant sweet alyssum alongside one vegetable bed as a banker plant for beneficial hoverflies and parasitic wasps.
For more on natural pest management, check out our free Garden Planning Guide at Your Garden Toolkit.
Frequently Asked Questions
Do marigolds repel garden pests?
Mostly no. Marigolds can suppress root-knot nematodes when grown as a cover crop, but UC IPM found no reliable evidence that their scent repels aphids, whiteflies, hornworms, or other common garden insects. Some studies even show marigolds attract spider mites and slugs.
How do marigolds actually help with nematodes?
French marigolds (Tagetes patula) produce alpha-terthienyl, a compound toxic to root-knot nematodes. To work, they need to be grown as a solid cover crop for at least two months before being tilled in, not just planted as a border.
Will planting a few marigolds among my tomatoes protect them?
No. A few marigolds tucked between vegetables will not meaningfully reduce nematode populations, and a ring of marigolds around raised beds is not a pest management plan.
What should I plant instead to manage garden pests?
Rely on integrated pest management and encourage beneficial insects with a diverse mix of flowering plants such as sweet alyssum, yarrow, and California buckwheat, which attract predatory insects that eat pests.
