Marigolds interplanted among vegetables control root-knot nematodes.
This claim doesn’t hold up. Refuted A person has checked it against its sources.
The planner won’t plan around this claim. What is known instead is below.
What is actually known
Tagetes patula suppresses Meloidogyne spp. via alpha-terthienyl and related thiophenes. Suppression requires a dense sole-crop stand held for a full season, i.e. a biofumigant cover crop. Scattered marigolds among vegetables do approximately nothing.
When this applies to a garden, Milpa says: Marigolds do suppress root-knot nematodes, but only as a solid stand grown for a full season as a cover crop. Dotting them between your tomatoes will not do it.
The evidence
Evidence: checked against 1 source in the research-based literature.
The source
Does marigold have an effect on plant-parasitic nematodes when grown in an intercropping setting? Probably not.
Plants it applies to · 1
Folklore it answers
How this rule has changed
Every change is dated, newest first. The full record, with each reason, is in the data download.
- Wording made clearer
- Wording made clearer
- Details updated
- A person read the sources and confirmed it
- Added to the rules
Marigolds repel most garden pests and protect the whole garden. · What can I plant now?
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Cite this page
Milpa Gardens. “Marigolds interplanted among vegetables control root-knot nematodes.” Evidence grade: Refuted. https://milpa.garden/rules/marigolds-interplanted-among-vegetables-control-root-knot/
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How we grade evidence
- Well established
- The rule names its mechanism and is settled, by sources a person has read and checked or by plain arithmetic and geometry.
- Promising
- The mechanism is named and the literature backs it. A few questions are still open.
- A good hunch
- Plausible by its mechanism, but field studies are thin, so treat it as a lean.
- Contested
- The evidence points both ways, or no study has tested it, so the planner does not enforce it.
- Refuted
- The claim did not survive its sources. It is kept so the folklore can be answered.