French marigold
Tagetes patula L.
Botanical family: Asteraceae
A small annual Asteraceae native to Mexico (Tagetes patula), and not to India, despite its French name, the French marigold flowers abundantly all summer in the sun. Its roots release compounds (including α-terthienyl) that suppress certain soil nematodes, an effect most marked in a dense, prolonged crop. Easy and free-flowering, it's a classic of vegetable-garden edgings.
Full sun
Any soil
Moderate: water freely in dry spells
Annual
Role in permaculture
Tagetes patula releases α-terthienyl through its roots, a nematicidal compound shown against Meloidogyne and Pratylenchus (Gommers 1972, Ploeg & Maris 1999).
Good companions
Cover the soil (moisture, fewer weeds)
Traditional companion planting (benefit not demonstrated)
Insects attracted or useful
Documented synergies
Relationships backed by a named source, with their real scope. A synergy without a named reference has no place here, no “it is said that…”.
Its roots exude α-terthienyl, a molecule that kills root-knot nematodes through oxidative stress, the mechanism is well established. BUT beware of the most widespread myth: sowing a few marigolds among your tomatoes does NOT work. The research services are categorical, the effect is only obtained in a DEDICATED and DENSE stand, over a whole season, on the site of the future crop. It targets only root-knot and lesion nematodes (it may even favour others), depends on the species (the French marigold, Tagetes patula, is the most effective), and only the living roots act, not a marigold mulch.
scientific study
- · UF/IFAS Extension ENY-056, Marigolds (Tagetes spp.) for Nematode Management
- · Nematicidal actions of the marigold exudate α-terthienyl (2019), Biology Open 8(4):bio038646, DOI 10.1242/bio.038646
Seasons & availability
Flowers from June until the frosts; sown in spring, in March under cover or in April and May outdoors once frost is past, with flowers picked all summer.
Available: June, July, August, September, October.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Plants For A Future, « Tagetes patula » (pfaf.org/user/Plant.aspx?LatinName=Tagetes+patula)
- Missouri Botanical Garden, « Tagetes patula » (plantfinder.mobot.org/PlantFinderDetails.aspx?taxonid=277481)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Secondary medicinal use.
Family behaviour: Asteraceae
In general, Asteraceae are a family rich in flowers appreciated by pollinators and beneficials (pot marigold, yarrow, chamomile). It is very scattered, from the mildest lettuce to the allelopathic sunflower.
Understanding families means learning one rule per family rather than every pairing one by one. Learn more →
Species & varieties
The best-known species and varieties in France.
Species
Voices of peoples
Paraphrases attributed to their documented sources. Never an invented quote.
Nahuas of the Valley of Mexico, described by the Franciscan Bernardino de Sahagún · Valley of Mexico, 16th century (Florentine Codex, written c. 1540–1585)
Among the Nahuas, the Tagetes flower is called cempoalxochitl, 'flower of twenty' (from cempoalli, twenty, and xochitl, flower), echoing its abundant flowering. Sahagún documents it in the Florentine Codex: it accompanies the ritual dances, thus the feast of Tecuilhuitontli, where women danced holding strings of flowers, and the offerings. Its link with the dead is attested from pre-Columbian times. On the other hand, its role in the Catholic Día de Muertos belongs to a later blending: two strata that should not be confused.
Bernardino de Sahagún, Historia general de las cosas de Nueva España (Codex de Florence), v. 1540-1585 ; synthèse Mexicolore, fiche « Cempoalxóchitl »
A fact attested by a 16th-century primary source. The pre-Columbian funerary meaning and the modern Día de Muertos feast are two distinct strata, presented here separately. No medicinal use is put forward here.
Keep in mind
The nematicidal effect is solidly documented, but only in a full, dense crop, over a whole season, ideally as a preceding crop (before tomatoes for example), not as a mere occasional companion around crops. The protection against the whitefly is also documented: the French marigold emits limonene, which reduces whitefly settlement on the neighbouring tomato (Conboy et al., 2019, PLOS ONE), an effect that works when the marigolds are in place beforehand, less clear if the infestation is already established.
A note on rigour: many companion pairings are gardening folklore; this note sums up what the sources say, where there are any.
Key takeaways
- • Prefers full sun exposure.
- • Ideal soil: any soil.
- • Classic companion: Courgette (zucchini).