Onion
Allium cepa L.
Botanical family: Alliaceae
Allium cepa, one of the oldest domesticated plants (Sumerians 4000 years ago). Grown as yellow onions (Auxonne, Tropea), red (Brunswick), or white. Two possible methods: sowing (April-May, harvest October, long keeping) or planting sets (March, harvest July-August, simpler). Keeps 6-9 months in a cool cellar after drying on a rack.
Full sun
Light, well-drained
Moderate
Hardy: winter onions (known as Japanese onions), planted in autumn in soil that does not stay waterlogged, overwinter in the ground
Overwinters in your zone
Role in permaculture
The sulphur compounds released by the bulbs are reported to repel several pests (the carrot fly in particular), an effect documented in the laboratory, moderate in the garden. Like the other alliums, tradition keeps it away from legumes, with no effect on their nodulation demonstrated in the field.
Good companions
Attract pollinators and beneficial insects
Traditional companion planting (benefit not demonstrated)
Poor companions
Traditional avoidance (antagonism not demonstrated)
Insects attracted or useful
Known pests & diseases
Pests and diseases that commonly affect this plant, tap to learn how to recognise and manage them.
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…”.
The flip side of the carrot–onion pairing, just as well measured: grown together, the carrot reduces thrips attacks on the onion, while the onion protects the carrot from its fly. A real but moderate mutual benefit, a help, not an absolute barrier, and all the more useful as it combines with rotation and good sowing timing.
scientific study
- · Uvah I.I.I. & Coaker T.H. (1984), Entomologia Experimentalis et Applicata 36(2):159-167, DOI 10.1111/j.1570-7458.1984.tb03422.x
Seasons & availability
Fresh onions in summer; keeping onions all year round.
Available: January, February, March, April, May, June, July, August, September, October, November, December.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- RHS, « How to Grow Onions » (rhs.org.uk/vegetables/onions/grow-your-own)
- La Ferme de Sainte Marthe, « Réussir la culture des oignons » (fermedesaintemarthe.com/en/blogs/comment-reussir-la-culture-de/reussir-la-culture-des-oignons)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Sometimes difficult to digest raw; may irritate sensitive people.
In the kitchen & the apothecary
Where to find onion in preparations: recipes and traditional herbal teas.
Family behaviour: Alliaceae
In general, Alliaceae form sulphur-rich bulbs (garlic, onion, leek, chives, shallot). Their smell is reputed to confuse some pests; the effect has been measured against the carrot fly while the onion is young (Uvah and Coaker, 1984).
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.
Common varieties
Voices of peoples
Paraphrases attributed to their documented sources. Never an invented quote.
Plutarch (Greek author, 1st–2nd c. AD), describing the Egyptian priests · Egypt (Greco-Roman gaze)
In the De Iside et Osiride (ch. 8), Plutarch writes that the Egyptian priests keep away from the onion and carefully avoid it, because it would be the only plant to thrive when the moon is waning; he adds that it suits neither fasting nor feasting, since it causes thirst in the one case and tears in the other. The rejection of the onion by a religious class is therefore well attested, but the explanation (lunar cycle) is as much the speculation of the Greek priest-scholar as an Egyptian doctrine.
Plutarque, De Iside et Osiride (Moralia), ch. 8 (texte primaire ; trad. Loeb)
Attested: a priestly prohibition/aversion towards the onion. Caution: a late Greek source, more than a millennium after the pharaonic peak, which interprets Egypt from the outside. It is not a generality ('the Egyptians hated the onion') but a priestly taboo, even though the onion was a common food of the people.