Growing onions in the subtropics
With our mild frost free Winters and warm wet Summers, onions generally don’t do well in the subtropics. They are cool-weather growers, and need a bit of chill to form bulbs. I have tried about six different varieties from seed, plus leeks and chives, and have had good results only from white bunching onions, meaning that these might be the subtropical onions for me.
Growing onions: is it worth it?
I think of onions (like potatoes) as one of the vegetables that are so convenient to buy they are mostly not worth the effort of growing. They are cheap, always available, and store well in the pantry. The exception is green onions (and new potatoes) which are so much nicer when they are freshly pulled from the garden for a meal. Growing onions gives you the convenience of fresh green onions when you need them.
We have been using them in Japanese – style hotpots through winter, which are traditionally made with an onion called negi, which is a bunching onion, so a bit bigger and milder than a spring (green) onion. Apart from hotpots, fresh green onions are to my taste better for salads, omelettes, frittatas, soups etc, where you want the fresh onion taste rather than the caramelised flavour that brown onions provide so well.
For the hotpot, by the way, you slice them on a diagonal about 2 cm long, white and green parts, and add them to the boiling base about 5 min before serving.
So it’s handy that the one type of onion that seems to grow well here is the bunching type. They are like giant chives, and never form a bulb but rather divide to form clumps. The individuals are about 3 cm thick, with a long white stem, and are quite sweet. To harvest you gently pull one away from the clump, which keeps on growing. As you can see from the pictures, once the bed gets established it is self-shading and easy to keep weed free.
If you’re thinking of trying them, have patience. You may have more immediate success, but mine were sown in a tray, then planted out into an unfavourable (poor soil, too dry) bed where they struggled through the first Summer, then transplanted to a bed that was well prepared with old leaf mulch and lime where they finally took off. Their proof was when they finally began to divide, meaning that they should provide a constant crop for a while now.
A final word on transplanting onions; they transplant very well, and don’t compete well with weeds as seedlings. So don’t be afraid to grow your onions on until they are a good size before transplanting, even if you have them in a starting bed. The old idea of planting ‘sets’ is a good one.