Grow onions

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Last updated March 2018

Bulb onions
Shallots
Pickling onions
Spring/bunching onions
Oriental/Japanese bunching onions
European Welsh onions
Grow onions from sets or seed?
Harvesting and storing onions
Thinking of showing onions?
How to exhibit onions

Bulb onions

All types of onion (Allium) do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times
For a crop in June/July – sow winter-hardy types during the previous summer or set them in autumn. Only some types are suitable for storing, so check when buying.

For a storable crop in August, sow in winter/early spring or set in spring.

Spacing

Grow at the spacing necessary for the bulb size required. There’s no need to leave a huge gap between each plant if you only want small bulbs to use immediately, or want to harvest early before they reach full size.

For example, for a crop of onions that are about 5cm (2in) across, space them 5cm (2in) apart in rows that are 25-30cm (10-12in) apart.

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Shallots

Shallots have a delicate flavour and when peeled they divide into two or more segments, similar to garlic. You can use the leaves in the same way as spring onions.

All types of onion do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times
For a storable crop in August, sow or set in early spring, or set in winter.

Spacing
Grow 15cm (6in) apart, in rows 20cm (8in) apart for small sets; 30cm (12in) apart for large sets.

Buy shallots from Dobies, Sarah Raven, Suttons Seeds, or Thompson and Morgan .

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Pickling onions

You can use any small onion for pickling, including Spanish and red varieties, but the two most commonly used are shallots (see above) and pickling (or ‘baby’) onions. Why small? Because you can pack small ones more tightly into a jar.

All types of onion do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times
For a storable crop after two months’ growth, sow in the spring.

Spacing
Grow 1.5cm (1/2in) apart in rows that are 30cm (12in) apart.

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Spring/bunching onions

Spring or bunching onions are types of bulb onion that can be close grown and harvested young, when there is the hint of a bulblet at the base. These can be pickled too.

All types of onion do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times
For an early spring crop, sow winter-hardy types late in the previous summer.

For successional cropping after two months’ growth, sow in spring and then every few weeks to benefit from a continuous harvest.

Spacing
Grow 2.5cm (1in) apart, in rows that are 10cm (4in) apart, or in a bands about 7cm (3in) wide and 15cm (6in) apart.

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Oriental/Japanese bunching onions

Oriental or Japanese bunching onions are similar to spring onions but are derived from Welsh onions, so are hardy perennials for year-round growing and harvesting.

All types of onion do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times
For an early spring crop, sow winter-hardy types in the previous autumn.

For cropping the leaves or the later-maturing non-bulbing stems, sow in spring and every few weeks for a continuous harvest.

Spacing
Grow up to 15cm (6in) apart, in rows that are 30cm (12in) apart.

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European Welsh onions

European Welsh onions (Allium fistulosum) look like sturdy spring or bunching onions, but are evergreen hardy perennials, so they have the advantage of providing a leafy crop during winter (down to around -10 degrees C). You could find a permanent spot for them, or grow them as annuals if preferred.

Buy seed from Thompson and Morgan. Alternatively, beg some divisions from someone who has too many on their allotment.

All types of onion do best in well-drained fertile soils in open, not shaded, sites.

Growing/harvesting times

For a perennial crop of leaves and stems for all year round, sow in spring or summer. Eat the leaves and the stem bases as you would spring onions – either raw or cooked.

Spacing
Thin to clumps about 25cm (9in) apart in rows 30cm (12in apart). Divide every few years.

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Grow onions from sets or seed?

All onion types are available as seeds; sets are commonly available for bulb onions and shallots.

Seed

Growing bulb onions from seed gives you a far greater choice of variety, but seed must be sown as early as possible in spring. If the ground is wet and cold you have to delay sowing, unless you can sow directly under polythene, or use modules under cover for later transplanting after hardening off. 

A range of onion seeds is available from Dobies, Sarah Raven, Suttons Seeds, Thompson and Morgan .

Sets

Sets are available for maincrop small bulbs and shallots that have been grown and harvested early in the previous year ready for planting in late spring when the soil conditions should be good. Their shorter growing season and reduced susceptibility to dry conditions, weeds, pests and diseases make them popular with many kitchen gardeners as a reliable way of getting a good crop with little effort. A wide variety of sets are sold by Dobies, Sarah Raven, Suttons Seeds, Thompson and Morgan ,!– and
Unwins–>.

Bolting
Many varieties of onion are prone to bolting (ie producing a flower stem) if their growth is checked by cold weather. The plant thinks the cold snap is winter and moves prematurely into its second phase of growth, which is to flower and die. Seed-sown onions are more vulnerable than sets because of their longer growing period, but late cold snaps can still affect sets. Heat-treated sets are much less prone to bolting and are supplied at the correct planting time (late March or April).

Onions with resistance to bolting

Winter hardiness
Until relatively recently, overwintering bulb onions could only be grown from seed, but now autumn planting sets are available from some suppliers such as Dobies, Sutton Seeds,Thompson & Morgan . The sets are dispatched in autumn for immediate planting, for summer cropping.

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Harvesting and storing onions

Drying off
Once onions have finished their growing cycle, the leaves naturally begin to bend over at the top of the bulb before yellowing. At this stage gardeners can help the ripening process by gently forking beneath each bulb to disturb the roots. In good weather, the onions can be left on the ground to dry off, but in wet weather they should be placed on racks under well-ventilated cover.
Storing
They should then be stored in a cool airy place that’s not too humid, otherwise the bulbs will eventually rot or sprout leaves. Place them in nets or hang them up in old tights or weave the necks into strands of raffia.

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Thinking of showing onions?

A keen competitor
We spoke to Martin Davis at the Newent Onion Fayre in 1999.
He told us that he had been growing vegetables for 20 years before he thought of showing. He’d visited a show about 10 years before and thought that he could do better, entered his first show, was placed, and caught the bug. He now grows onions, shallots and carrots to exhibit and to eat.

‘Make no mistake about it, it’s a fallacy that show vegetables are inedible. In fact they’re very good to eat,’ he pointed out. ‘For example, ‘British Bulldog’ that I’ve won with at the Newent Onion Fayre this year is a very tasty solid onion that’s sound inside. It’ll keep for a good six months too.’ He added, ‘Showing is a great hobby and I love meeting familiar faces and exchanging banter. It’s very good-humoured and fun to be part of.’

Tips for showing…and winning

How do you start? Visit a few shows and talk to exhibitors and officials to find out more about entry and presentation rules. You’re half-way to winning if you read the schedule carefully and comply with the conditions. And a copy of the RHS Show Handbook helps enormously (try Waterstones or directly from the RHS).

Roy Haviland, who was judging that day, also advises, ‘It may sound obvious, but follow the rules to the letter. Often I can’t judge an entry because it doesn’t comply. If the class is for five onions, then make sure that you enter five. And for collections, be sure to check that each group is within or above the weight limit, as set out in the schedule. With strings, there are no RHS rules to follow, but it’s essential that the onions hold together however they are lifted up. The string should contain the specified number of onions too, which are judged on uniformity.’

He also added a tip for aspiring judges – if you’re asked to judge flavours, make sure that you only taste the large onions – they’re much milder than the small ones.

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10. How to exhibit onions

How to stage your onions
Exhibiting onions at a show sounds simple, but of course nothing ever is. How do you get from onions in the ground to onions on the show bench?

Really it all begins a year in advance when you should browse around a horticultural show to see what you’re aiming for. As we said on the previous page, talk to some exhibitors to find out what, how and why they’ve prepared (dressed) their exhibits. If you can’t get to a show, join your local horticultural society (the local library will have details) and pick the members’ brains there.

Perfection begins at the growing stage, so you should be careful with watering to avoid splitting from sudden surges in growth, and be sure that the top growth is upright so that you have that all-important straight neck on display on the show bench. A lop-sided top does not win prizes. Medwyn Williams is the man for advice on growing for showing.

Once you’ve lifted your precious crop, it needs to dry off, and then the papery layers need rubbing off to reveal a perfectly intact skin. The other area for attention is the top, which is tied round and round with raffia (for onions).

At the shows we’ve seen, the onions have been staged on special collars or rings for stability, but it’s also possible to set them into sand.

We’ve never shown produce, so the above information is what we’ve picked up in passing. For detailed methods and timing, find someone with experience, and don’t forget to read that show schedule too.  First, look at Newent Onion Fayre’s information on growing and showing onions at their event. Also visit the National Vegetable Society’s Growing for Showing webpage, with plenty of growing tips, and Growing Large Onions has useful information too. For ‘dressing’ the onions ie preparing them for the show bench, the RHS forum thread on showing onions is useful, as is this Growing Large Onions plus the How I dress the Exhibition Show Onions video, which shows you how to tie them. You can also chat to local garden society members but do check with a regular exhibitor that the methods mentioned are acceptable for your target show (you don’t want to be disqualified by using ‘illegal’ tricks).

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