Allium adventures Are onions good value to grow?

Onions are versatile vegetables but is it worth the time and effort it takes to grow them? Lynda Hallinan puts it to the test in a seed-to-plate trial.

From spring onions for salads to long-keeping varieties and French shallots, onions are a staple crop. But despite their culinary versatility, they’re not exactly easygoing in the garden.

An apple a day keeps the doctor away, but an onion a day? That improves almost every meal. Rare is the day in my house that an onion isn’t sliced, diced or pickled, as the majority of my favourite savoury recipes begin with “saute a finely chopped onion…”

I buy more onions than any other vegetable. As a family of four, we eat at least 1kg of onions each week – more now that my 10-year-old son Lucas has developed a taste for raw red onion.

As we live on the outskirts of ‘Pukekohe Long Keeper’ country, onions are sinfully cheap to buy in bulk, especially when commercial growers donate them to community fundraising events. When you can buy a 10kg sack of perfect onions for as little as $10, it seems ridiculous to waste your own time, energy and garden space growing your own. Except, of course, that by growing your own, you can harvest several sackfuls for the price of a packet of seed, and you can decide if you want to use fertilisers and sprays – organic or otherwise – to improve your yield.

But let’s not pretend that onions are easy for everyone to grow. Not only do onions need a fair bit of soil, they hog this space for the entire growing season. I spent eight months fussing over the finicky specimens in this story, worrying about spring weed competition and summer drought and autumn fungal problems. I’m not convinced I want to ever voluntarily repeat the process, although I was surprised how easy spring onions were to grow in comparison to their fat-bottomed friends. (Plus, if you leave spring onions in the ground for long enough, they generally do eventually produce baby bulbs.)

When I asked on Facebook if any gardening friends had had better luck with onions, most hadn’t. “Easier to buy them,” was the consensus. Sue Rackham nailed it when she told me that “good drainage and good luck are both essentials.”

But my friend Emma, who once dated an onion farmer, piped up with useful (with the benefit of hindsight) advice. “Onions have a surprisingly deep root system, so you need to work the soil deep – at least 25cm – to ensure good drainage. Sorting the drainage is important as the soil will end up compacted due to them being in the ground for a long time. Onions are gross feeders and do well with regular fertilising with Nitrophoska Blue (N-P-K 12-10-10) and lime between seaPsHoOnTsO.”S:

Oops. I barely dug my soil over. I weeded an area that had previously been home to a green manure crop, added fertiliser and mulched the rows after transplanting, but if I knew then what I know now, I’d have got the rotary hoe out – or at least put in a little more gruntwork with my spade – to improve the drainage.

I should have consulted my trusty 1926 Brett’s Gardening Guide. “The best onion soil is a deep rich loam of a somewhat sandy texture, but well-worked clay, with plenty of lime, bonedust and wood ashes added, will produce an excellent crop. The soil must be well-drained and prepared by deep digging.”

In Alexandra, Lenore Townsend reckons onions are easy because “our soil is sandy and water contains lime. We grow sufficient to last all year, red and white. It’s important to dry them off properly and store in onion bags.”

Sandy soil also benefits Philippa Edwards in her coastal garden near Bulls. “We plant onions on raised rows and, after two weeks, give them a weed and cover the soil with lawn clippings. We cover with bird netting as soon as they are planted or they need to be replanted daily.”

Dig in general garden fertiliser prior to planting, and top up with monthly