Page 12 - Simply Veg 4 2022

Japanese Onions or Autumn Sown Onions
KELVIN MASON FNVS
Members may remember that Raymond Higgins carried out a survey for the trustees in 2019 from which we had some requests for articles on certain topics in Simply Vegetables, one of the requests was for growing Japanese onions hence this article. I will work my way through some of the other requests next year, sorry for the delay.
Onions are a main ingredient in many recipes especially soups so are widely used in the kitchen, and it is helpful to have an all the year-round supply. One way of achieving this is to grow Japanese onions to fill the gap usually June to September between stored onions of the previous year and the next crop due in September.
Japanese onions were bred in Japan hence their name, they are very hardy
and will overwinter outside without any protection. They are sown or planted in
the autumn which is where their other name comes from and are ready to harvest in June / July the next year. The main disadvantage of these onions is that they will not store for long usually about two months, three at the most; but they provide a crop until the maincrop onions are ready. With good storage and growing both maincrop and Japanese onion it is possible to have home grown onions all the year.
These onions are what are classed as intermediate day-length and hardy which is why they grow overwinter and are usually bolt resistant. They start to bulb up when they day length is 12 hours (at the end of March) whereas the normal onions do not bulb up until the day length is 16 hours which is usually in June time. If the bulbs are larger than 15mm dia in December, January or February they are large enough to initiate a flower bud and will therefore bolt, hence the reason for the late sowing. Small bulbs will not initiate a flower bud.
They need less light than the normal onion cultivars grown which is why they will grow overwinter although they do
not make a lot of growth until March.
They are not affected by the short days which the normal onions are and if sown in September would go straight to seed
in the next summer. The timing of sowing or planting is fairly critical and varies depending on which part of the country you live. The aim is to get plants large enough to survive overwinter but not too large or they can be triggered to produce a flower spike.
Sowing/Planting
Japanese onions can be purchased as sets or seed, and the seed can be sown in rows directly into the soil or sown into seed trays or modules and pricked out into modules grown on before planting out.
The recommended sowing dates are: • NorthernEngland,NorthWalesand Scotland the 2nd week of August
• Midlands and Eastern England 3rd week of August
• Southern England and South Wales 4th Week of August
If sowing on the vegetable plot lightly fork over the area, rake to a fine tilth, and take out a drill 1cm deep using a line to
Ready to harvest
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keep it straight. Sow the seed thinly to save thinning and cover with fine soil firming into place with the back of a rake. If the onions do need thinning leave this until March in case, there are any losses over winter. Rows should be 25 to 30 cm apart for both seed and sets, the sets should be planted 8 to 10cm apart leaving just the tip of the set above soil level. Use a trowel or dibber to plant as just pushing the sets into the soil can damage the base also when the roots start to grow, they can push the set out of the soil if the soil is firm. Seed takes 7 to 10 days to germinate. If the soil
is still dry from the summer (it may be
this year!) water the drills before sowing and allow to soak in. if the weather is very hot germination can be poor so sow in a shaded area and keep moist to keep it cool.
If sowing in seed trays (or recycled meat trays) sow reasonably thinly as they will be pricked out soon after germinating. Cover the seed lightly and make sure the
growing media is moist. Put the trays in a cold frame, cold greenhouse, or a sheltered spot outdoors, they do not need heat to germinate. If sowing in modules sow 2 /
3 seeds in each module, these can be left as multiple seedlings for smaller onions
or thinned to one seedling if larger onions are required. Prick out when the leaves are at the crook stage (when they are bent at 90° angle) or soon after (I do mine when they have straightened out, they are easier to handle), put into 5 or 7cm modules. Keep them in good light but do not force them and grow them at normal outdoor temperatures.
Planting
Plant the seedlings or sets into a bed that has been deeply dug (unless a no-digger!) or deeply mulched if a no-digger. They are best grown in soil that has been manured for a previous crop and not freshly manured, if the soil is poor a small amount of compost can be added before planting.