If you see ‘Japanese onions’ on seed packets or a bag of sets, you know you’ve got some tough cookies. First bred in Japan, they’re hardy and resilient overwintering varieties that will grow outside uncovered over the next few months, then provide you with lots of large, crisp bulbs at the end of next spring. They need less light that other onions, so will grow through the short days of winter and early spring.
As their growing season is the opposite to many other crops, they don’t take up space in summer when you want to leave room for more tender veg, so they’re a great crop to give space over to in winter.
Right now is the time to start sowing seeds of these onions, either in trays for planting out in late September – which gives you a little control as to their growth – or into relatively light, well-draining soil on your plot. Sow seeds thinly in well-raked soil, but don’t add fertiliser or it may encourage susceptible young foliage too soon. Cover lightly with compost and water in, then thin out seedlings in early spring next year.
In a month or so you’ll also buy onion sets to plant out, but there’s more fun in growing seed, and you can control the plants’ growth into solid little bulbs, which don’t bolt too soon, either.