Allium cepa
Amaryllidaceae
Onion
Large bulbs with 4-6 hollow, cylindrical leaves. Flowers are umbells with large pedicels. Pale green perianth.
Uses
Most onions are harvested when the foliage has died down. Some varieties, such as Spring Onions, are picked while the foliage is still edible.
Bulbs can be stored in a cool dry position.
Used in many different dishes. Can be eaten cooked or raw. Vegetable.
Culture
Preferred temperature range is 13-25 degrees C.
Requires a relatively dry situation - low humidity, good drainage and few irrigations.
Friable soil will promote large bulbs. Will respond better to organic fertilisers than slow release fertilisers. Requires high levels of nitrogen and potassium, and a pH of 6-7.
Propagation
Propagated by seed and division of bulbs. It may be easier to grow seedlings rather than direct sowing seeds.
Cultivars
There are many hundreds of onion types available including brown, white, yellow, purple and red varieties - each with many cultivars within the variety.
Plant Health
Can suffer from aphis, thrip, maggots and cutworms. Encourage air movement around the foliage to reduce fungal problems.
http://osu.orst.edu/Dept/NWREC/onionb-w.html
More info
'Home Vegetable Growing' and 'Commercial Vegetable Production' courses through Australian Correspondence Schools, see www.acs.edu.au/hort.
'Commercial Hydroponics' on CDROM from Australian Correspondence Schools, see www.acs.edu.au/shop