Why you shouldn’t grow onions on your allotment — but if you do, go for these really exceptional ones

Mark Diacono takes a look at allotment logic, and shares his formula for what you should and shouldn't spend your time and energy growing.

Many years ago, I was helping a friend clear a long-unused allotment. Towards the end of the day, an elderly gentleman — we later learned he had been there longer than anyone — came over and offered us a bag of turnips.

They were the best turnips I’d ever seen.

I asked why he would give away so many well-grown vegetables? ‘I don’t really like them, but you’ve got to grow turnips haven’t you?’

This train of thought is exactly what has great swathes of most allotments and kitchen gardens given over to onions. The logic is compelling — most of us use them more days than not — but there is nothing you have to grow: if you are short of time, inclination or space, you should seriously consider whether you grow onions. Or certainly which onions you allow into your garden.

Without infinite resources, something has to give and, right at the centre of the Venn diagram of ‘cheap to buy’, ‘disease prone’, ‘in the ground for ages’ and ‘little upturn in flavour when homegrown’ is what does it for me. I grow no main-crop jacket spuds, no late-season carrots and it’s a polite ‘no thank you’ to bog-standard white onions.

But there are onions that are worth growing: I prioritise shallots and red onions. I say ‘red onions’, but of the many lies we are told as kids, few endure as unquestioningly as red onions. ‘Red’ onions are purple, for heaven’s sake. The same person must have named sweetbreads.

Compared with white onions, red varieties often have a more agreeable flavour, especially when used raw, and they tend to be sweeter when roasted — and, of course, reds are more expensive to buy. I usually grow a couple of varieties — a little edible insurance, in case the growing season favours one or a pest prefers another — and ‘Piroska Red’ is a constant, being reliable, a long storer and delicious.

The case for growing shallots is even stronger: they are not cheap to buy, have a gentler yet more refined flavour than white onions and they are spaced more closely than onions: you get more in so many ways for your investment. ‘Jermor’ and ‘Longor’ are my favourite varieties.

Expensive to buy, shallots, such as the delicious ‘Jermor’ variety, are easy to grow at home, planted in full sun with good drainage.

Onions and shallots are easy to grow, as long as you take care of the few essentials. They like full sun and good drainage to do well; anything less is likely to impair steady development and cause them to bolt. Keep them weed free: this is partly to prevent nutrient competition, but more to promote good airflow, which helps minimise disease. A careful hoeing when the sun’s out should be enough to guillotine and desiccate most weeds. Do this and rotate where you grow alliums each year and you have every chance of a healthy harvest.

Onions and shallots can both be grown from either seed or mini-onions known as sets. Sets are easier to handle, but seed is considerably cheaper: the choice is yours. Plant sets and sow seed during the first half of spring: plant sets with the tips a little below the level of the soil and direct sow thinly in lines. Whether sets or seed, space shallots 8in apart and allow 1½–4in apart for small onions or 6in–10in apart for larger ones.

As onions and shallots mature towards the second half of summer, the leaves yellow. Lift them carefully with a fork when a few dry days are forecast and let them dry in the sun for a couple of days. Sort carefully through the harvest and discard any that are soft, then use any that are blemished quickly.

A trick I learned years ago was to use pairs of tights to store onions, with a knot tied between bulbs: hang them up on a nail and start using them from at the toe end, snipping below each knot as you go. Stored in the light, onions and shallots should be good for six months.

After all that, I do have a confession: I do grow some white onions, but rather than take up valuable space at the busiest time of the year, they are overwintering varieties. Planted in September or October when there is more space in the kitchen garden, they grow through the cold months, to harvest and free up space in late spring and early summer. Overwintering onions don’t store well, so lift them as needed, and use them immediately. ‘Radar’ is hard to beat for cold-weather growing.

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