384 Handbook of herbs and spices
developed there (Currah and Proctor, 1990). In cultivars where flowering can be
induced, a cool period of 40 days at 14 ∞C is required. Although seeds can be
produced from some lines, vegetative multiplication is usually practised. The CO
cultivars are pink or red in colour. The multiplier onion splits into several daughter
bulbs, ranging in number from 4–8 to 8–10. Both multiplier onion and tropical
shallots take only 60–75 days to multiply and die down again, and the bulbs can be
stored for considerable periods (over five months). Individual clusters of multiplier
onion in the CO series have an average weight range of 25–85 g. Other cultivars
reported from Indonesia are Ampenan, Cloja, Bima, Kuning, Bauji, Balijo, Suminep,
Bawang Lambung, Betawi Cipanos, and Hajakuning.
22.8.2 Climatic requirement
An average temperature of 25–32 ∞C is optimum during the growing period of
shallots. Jenkins (1954) reported that high temperature favoured bulbing. Plants
grown at temperatures of 21 ∞C and higher all formed bulbs, but larger bulbs were
produced with a 15-hour photoperiod than with a 10-hour photoperiod. When the
temperature was lower than 21 ∞C, no bulbs were formed regardless of day length.
22.8.3 Soils
Shallots can be grown in all types of soil with a pH of more than 5.6, however, well-
drained alluvial soils are preferred for better growth and development. Kusumo and
Muhadjir (1987) grew shallots traditionally after the harvest of the rice crop on raised
beds of subsoil obtained from the deep furrows. However, seed origin and soil type
had no significant effect on yields.
22.8.4 Propagation
With a few exceptions, shallot is currently propagated vegetatively in most parts of
the world. Vegetative propagation has until now been dominant in shallot culture
throughout the world (Currah and Proctor, 1990). When grown from sets, the shallot-
growing season is relatively short, thus enabling production where onions from seed
cannot produce economic yields of commercially acceptable sized bulbs. However,
when grown from seed, hybrid shallots with strong heterosis have a fast growth rate
and bear high yields after 3–4 months of growth. In more temperate lands, similar
practices are used in Europe, the USA and Argentina, where sets are transplanted on
raised beds at 25–40 plants m–2. Yields of vegetatively propagated shallots range
between 5 and 30 t ha–1 in Indonesia (Subijanto, 1988).
In Israel, 100% of the shallot grown commercially is propagated from seed. Krontal
et al. (1998) were the first to provide a scientific description of seedling development,
based on material derived from a nameless Thai landrace, Israeli Genebank accession
no. 66–1004. Seeds of tropical shallot are smaller than those of bulb onion, the 1000-
seed weights being on average roughly 2–3 g and 3–4 g, respectively. Seeds have no
dormancy and readily germinate when moisture is available. The black seed-coat is
crinkled and the seed is irregular in shape, like that of onion.
22.8.5 Planting
Three shallot crops are grown a year, the major seasons being April to August,