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Fact file: onions

Fact file: onions

BBC Gardeners' World Magazine

Published: Thursday, 22 August 2019 at 11:42 am

Discover fascinating facts and growing tips about this useful vegetable.

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A key ingredient of countless dishes, the onion is a storecupboard staple that is very easy to grow.

Find out all you need to know about growing onions in our onion Grow Guide.

Stored correctly, onions should last up to six months. For more ideas on ways to store harvests, take a look at our feature on how to preserve your harvests.

More allium-growing advice:

How to grow shallots
How to grow garlic in autumn (video)
How to grow overwintering onions (video)

Discover fascinating facts and growing tips about this delicious and essential vegetable, below.

Did you know...

White onions

Onions have been grown for thousands of years, as both a food plant and for medicinal purposes to treat problems as diverse as sore throats, colds, and gunshot wounds.

Nutrition

Onions are rich in beneficial, anti-inflammatory flavonoids and sulphur compounds.

Harvest

Onion pile

Freshly harvested white onions

Once the leaves begin to yellow and flop over, wait several weeks and during dry weather lift the bulbs carefully using a fork. Lay them in the sun for a few days or in a greenhouse, ideally on mesh or a table so air can circulate and dry the bulbs.

Store

Hanging onions

Hanging out red and white onions

Bulbs must be unblemished and thoroughly dry to avoid rotting. Brush off the soil, cut the leaves to within 5cm of the bulb, and store in net bags or tie into ‘ropes’ to hang up in a cool, dry, airy place. Here are our full instructions on storing onions.

How to grow

Planting onion sets

Planting white onion sets

Growing onions from sets is quickest, easiest and most reliable, though, raising onions from seed is cheaper and gives the widest choice of varieties. Grow in full sun on well-drained soil that is rich and fertile, but not freshly manured. Weed to avoid competition for water and nutrients. Crop rotation is important as onions are liable to several pests and diseases, particularly downy mildew, onion fly, stem eelworm and white rot. Throw away infected bulbs and avoid growing on the same site for eight years.

Our choices

Onion harvesting

Harvesting red onions in a raised bed

‘Hyred’, a late-maturing red onion producing well-storing onions in September; ‘Red Baron’, another red onion producing a large crop of well-flavoured onions; 'Setton', a white onion bearing high yields and storing well.

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