Food Plants International

240
Names
English: Bulb onion Scientific name: Allium cepa var. cepa L.
Tok pisin: Synonyms:
Tok ples: Plant family: Alliaceae
Description: A herb with a two year life cycle. Normally it
develops fattened bulbs at the base. It has a shallow fibrous root
system. The actual stem in very short and condensed. Leaves are
produced in an alternate fashion one after the other from the top
of this stem. Successive leaves grow up inside, then burst
through the leaf sheath of the previous leaf. Leaves are thin and
long. They are slightly to markedly flattened on the upper
surface. Long day lengths and warm temperatures help the leaf
bases become swollen and store food reserves. Flowers are
greenish white in colour. Flowers develop on a rounded head
with stalks all coming from the centre. Flowers in the rounded
head open irregularly. There are no bulbils on the flowerhead.
Distribution: It is more easy to get onions to grow and form
bulbs in the highlands in the tropics but they can be grown from
sea level to 2600 m altitude in Papua New Guinea. In Nepal they
grow to 3000 m altitude. They do not suit the wet humid tropics.
Because the day lengths are short near the equator, onions often
do not produce a bulb. Some newer varieties will yield in the
tropics. It suits hardiness zones 5-10.
Cultivation: They are grown from imported seed. For bulbs, a tropical cultivar is needed and
bulbing is normally better at higher altitudes. Cultivars which form flowers early need to be
avoided. Seedlings can be transplanted.
Production:
Use: The bulbs and leaves are used as flavouring raw or cooked.
Food Value: Per 100 g edible portion
Edible Moisture Energy Protein Calcium Iron proVit A proVit C Zinc
part % KJ g mg mg µg mg mg
Bulb 92.8 99 0.9 0.3 0 10 0.1
Leaves 90.0 1.4 0.5 0.5
Insects:
Agrotis ipsilon (Hufn.) Noctuidae (LEP) Black cutworm
Neotoxoptera formosana Takahashi Aphididae (HEM) Onion aphid
Oribius inimicus Mshl. Curculionidae (COL) Shot hole weevil
Thrips tabaci Lind. Thripidae (THYS) Onion thrips
Diseases:
Leaf tip withering Fungus Alternaria porri
Smudge Fungus Colletotrichum circinans (Berk.)Voglino
Soft rot Bacteria Erwinia carotovora
And Pseudomonas cepacia
Pests:
Importance: In Papua New Guinea, it is not widely grown but is popular and imported for sale.