Growing Onions in the Garden
Another crop in which the Japanese plant breeders have made a notable contribution is bulb, as opposed to green ‘spring’ onions. There has always been a gap, in June and July, in the supply of bulb onions from the garden. Onions and stored over the winter rarely last beyond April or May, while the maincrop raised by sowing seed or planting sets in spring is normally not ready for use until August.
Attempts are made to fill the gap by sowing fairly hardy, traditional English overwintering varieties in autumn — ‘Ailsa Craig’, ‘Reliance’ and ‘Autumn Queen’ for example — which mature a little earlier than spring-sown varieties. But it only works in fairly mild parts of the country and in reasonable winters. More often than not the onions bolt in spring, or are killed off by severe weather. These failings have been overcome in the new, hardy, Japanese overwintering onions, which after trials over a number of years have proved beyond question their reliability in this country. They mature in June and July.
The sowing time for the Japanese onions is fairly critical, as they should ideally be about 15-20cm (6-8in) high in October. If sown too early they become too large and may bolt in spring; sown too late they risk being too small at the onset of winter, and may not survive in very bad weather. The recommended sowing times are as follows: north of England — first week in August; Midlands and east of England — third week in August; south of England — fourth week in August.
Seed is best sown in situ (transplanting may lead to bolting), thinning to about 2.5cm (1in) apart in autumn, 5cm (2in) apart in spring. Give a top dressing of nitro chalk in spring (60-90g/2-3oz per m2). Harvest them like any other onions. But remember they are not ‘keepers’, and can only be stored for two to three months.
‘Express Yellow F1’, ‘Imai Early Yellow’, and ‘Senshu Semi-Globe Yellow’ are three good varieties.