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Amaryllidaceae FAMILY

Allium cepa

Allium cepa

Edibility
5/5
Medicinal
3/5

Safety & Hazards

There have been cases of poisoning caused by the consumption, in large quantities and by some mammals, of this plant. Dogs seem to be particularly susceptible[1].

Cultivation Details

HabitEvergreen Bulb
Growth—

Onions are best grown in a Mediterranean climate, the hot dry summers ensuring that the bulbs are ripened fully[2]. For best growth, however, cool weather is desirable at the early stages of growth[2]. Plants are frost-tolerant but prolonged temperatures below 10°c cause the bulb to flower[2]. Optimum growth takes place at temperatures between 20 and 25°c[2]. Bulb formation takes place in response to long-day conditions[2]. Prefers a sunny sheltered position in a rich light well-drained soil[3, 4]. Prefers a pH of at least 6.5[2]. Plants tolerate a pH in the range of 4.5 to 8.3. Plants are perennial but the cultivated forms often die after flowering in their second year though they can perennate by means of off-sets[3]. This species was derived in cultivation from Allium oschaninii[5]. Most forms are grown mainly for their edible bulbs but a number of varieties, the spring onions and everlasting onions, have been selected for their edible leaves. There are several sub-species:- Allium cepa 'Perutile' is the everlasting onion with a growth habit similar to chives, it is usually evergreen and can supply fresh leaves all winter. Allium cepa aggregatum includes the shallot and the potato onion. These are true perennials, the bulb growing at or just below the surface of the ground and increasing by division. Plants can be divided annually when they die down in the summer to provide bulbs for eating and propagation. Allium cepa proliferum is the tree onion, it produces bulbils instead of flowers in the inflorescence. These bulbils have a nice strong onion flavour and can be used raw, cooked or pickled. Most modern treatments are now referring to this form as Allium x proliferum, being seen as a hybrid with the Welsh Onion (Allium fistulosum). Onions grow well with most plants, especially roses, carrots, beet and chamomile, but they inhibit the growth of legumes[6, 7, 8, 9]. This plant is a bad companion for alfalfa, each species negatively affecting the other[9]. Members of this genus are rarely if ever troubled by browsing deer[10].

Propagation

Seed. Early sowings can be made in late winter in a greenhouse to be planted out in late spring. The main sowing is made in early spring or mid spring in an outdoor seedbed, this bed must be very well prepared. A sowing can also be made in an outdoor seedbed in August of winter hardy varieties (the Japanese onions are very popular for this). These overwinter and provide an early crop of onion bulbs in early summer of the following year. Onion sets can be planted in early to mid spring. Sets are produced by sowing seed rather thickly in an outdoor seedbed in late spring or early summer. The soil should not be too rich and the seedlings will not grow very large in their first year. The plants will produce a small bulb about 1 - 2cm in diameter, this is harvested in late summer, stored in a cool frost-free place over winter and then planted out in mid spring. A proportion of the bulbs will run quickly to seed but most should grow on to produce good sized bulbs. Cite as: Temperate Plants Database, Ken Fern. temperate.theferns.info. 2026-02-20. <temperate.theferns.info/plant/Allium+cepa>

Pollinators

Bees, Insects

References

  1. [1]Poisonous Plants in Britain and their Effects on Animals and Man. — Cooper. M. and Johnson. A. · HMSO · 1984 · ISBN 0112425291 ↩︎Concentrates mainly on the effects of poisonous plants to livestock.
  2. [2]The New RHS Dictionary of Gardening. 1992. — Huxley. A. · MacMillan Press · 1992 · ISBN 0-333-47494-5 ↩︎Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
  3. [3]RHS Dictionary of Plants plus Supplement. 1956 — F. Chittendon. · Oxford University Press · 1951 · ISBN - ↩︎Comprehensive listing of species and how to grow them. Somewhat outdated, it has been replaced in 1992 by a new dictionary (see [ 200 ]).
  4. [4]New Vegetable Growers Handbook. — Simons. · Penguin · 1977 · ISBN 0-14-046-050-0 ↩︎A good guide to growing vegetables in temperate areas, not entirely organic.
  5. [5]Alliums. The Ornamental Onions. — Davies. D. · Batsford · 1992 · ISBN 0-7134-7030-5 ↩︎Covers about 200 species of Alliums. A very short section on their uses, good details of their cultivation needs.
  6. [6]Companion Plants. — Philbrick H. and Gregg R. B. · Watkins · 1979 · ISBN - ↩︎Details of beneficial and antagonistic relationships between neighbouring plants.
  7. [7]Companion Planting for Successful Gardening. — Riotte. L. · Garden Way, Vermont, USA. · 1978 · ISBN 0-88266-064-0 ↩︎Fairly good.
  8. [8]How to Enjoy your Weeds. — Hatfield. A. W. · Frederick Muller Ltd · 1977 · ISBN 0-584-10141-4 ↩︎Interesting reading.
  9. [9]A - Z of Companion Planting. — Allardice.P. · Cassell Publishers Ltd. · 1993 · ISBN 0-304-34324-2 ↩︎A well produced and very readable book.
  10. [10]Perennial Garden Plants — Thomas. G. S. · J. M. Dent & Sons, London. · 1990 · ISBN 0 460 86048 8 ↩︎A concise guide to a wide range of perennials. Lots of cultivation guides, very little on plant uses.
  11. [11]Flora of China — Missouri Botanical Garden Press; St. Louis. · 1994 · http://flora.huh.harvard.edu/china/ ↩︎An excellent, comprehensive resource in 25 volumes. In addition to the botanical information the flora also gives basic information on habitat and some uses. An on-line version is also available.
  12. [12]Herbs — Phillips. R. & Foy. N. · Pan Books Ltd. London. · 1990 · ISBN 0-330-30725-8 ↩︎Deals with all types of herbs including medicinal, culinary, scented and dye plants. Excellent photographs with quite good information on each plant.
  13. [13]Sturtevant's Edible Plants of the World. — Hedrick. U. P. · Dover Publications · 1972 · ISBN 0-486-20459-6 ↩︎Lots of entries, quite a lot of information in most entries and references.
  14. [14]The Gardener's Assistant. — Thompson. B. · Blackie and Son. · 1878 · ISBN - ↩︎Excellent general but extensive guide to gardening practices in the 19th century. A very good section on fruits and vegetables with many little known species.
  15. [15]A Modern Herbal. — Grieve. · Penguin · 1984 · ISBN 0-14-046-440-9 ↩︎Not so modern (1930's?) but lots of information, mainly temperate plants.
  16. [16]Encyclopaedia of Medicinal Plants. — Chiej. R. · MacDonald · 1984 · ISBN 0-356-10541-5 ↩︎Covers plants growing in Europe. Also gives other interesting information on the plants. Good photographs.
  17. [17]The Herb Book. — Lust. J. · Bantam books · 1983 · ISBN 0-553-23827-2 ↩︎Lots of information tightly crammed into a fairly small book.
  18. [18]The Encyclopedia of Medicinal Plants — Chevallier. A. · Dorling Kindersley. London · 1996 · ISBN 9-780751-303148 ↩︎An excellent guide to over 500 of the more well known medicinal herbs from around the world.
  19. [19]The Complete Homeopathy Handbook. — Castro. M. · Macmillan. London. · 1990 · ISBN 0-333-55581-3 ↩︎A concise beginner's guide to the subject. Very readable.
  20. [20]Alternative Enterprises for Agriculture in the UK. — Carruthers. S. P. (Editor) · Centre for Agricultural Strategy, Univ. of Reading · 1986 · ISBN 0704909820 ↩︎Some suggested alternative commercial crops for Britain. Readable. Produced by a University study group.
  21. [21]Nature's Colors - Dyes from Plants. — Grae. I. · MacMillan Publishing Co. New York. · 1974 · ISBN 0-02-544950-8 ↩︎A very good and readable book on dyeing.
  22. [PFAF]Plants for a Future — pfaf.org ↩︎