Grow your own: Onions & Shallots

Mar 3, 2023

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These crops both belong to the allium family, which also includes garlic, but whereas onions form one large bulb, shallots split to form several small bulbs and are generally milder and sweeter than onions.

Onions can be grown from seed sown in spring for harvests in mid to late summer. They can also be sown in August and the plants overwintered for an earlier harvest in about July.

These summer-sown onions are often Japanese varieties. Onions can also be grown from sets, which are small immature bulbs, the best of which have been heat treated to prevent bolting (premature flowering) before the bulb has reached a good size.

Shallots are normally grown from sets, although seed is increasingly available (seed-raised bulbs tend not to split and instead form only one large bulb). Sets are planted in late February if soil conditions allow, otherwise in March/early April.

Varieties

‘Ailsa Craig’
An old favourite producing large bulbs. Great for the show bench, too.
‘Hi Keeper’
A good variety to sow in late summer/early autumn for overwintering as it is very hardy.
‘Red Baron’
Superb red variety with a beautiful mild flavour.
‘Electric’
An excellent red autumn planted onion.
‘New Fen Globe’
Produces large bulbs from early plantings.
Shallot ‘Pikant’
A good early variety that also stores well.
Shallot ‘Mikor’
Nice round shallots with slightly pink flesh. Eight to 10 bulbs per clump when mature in August.

Sowing & Growing Onions

Prepare the soil well, digging it over and raking. Scatter some Growmore or chicken manure pellets a week or two before sowing.

Rake over again and firm by tamping down with the rake and gently rake over again. Depending on the conditions of your soil you can start sowing as early as February but for most places in the UK, especially after a wet winter, it will be mid March, or April in Scotland, before conditions are favourable.

Onion seed: Sow seed fairly thickly along a groove about 13mm (1⁄2in) deep. Alternatively sow into trays for planting out later on.

Once the seedlings are through remove some to leave about 2.5-5cm (1-2in) between seedlings. Once the seedlings are larger and more upright thin them out again to about 10cm (4in) between them.

Take away thinnings as the smell could encourage onion fly. Japanese onions sown in mid summer are usually spaced a bit further apart.

Onion sets: Plant the small onion sets 10cm (4in) apart in rows 23cm (9in) apart with the tips just showing. Shallot sets: Plant these about 15cm (6in) apart with the pointed tip just showing above the surface of the soil.

Growing on onions

Once the bulbs are growing well, keep the rows free of weeds. Weed by hand if possible as bulbs are easily damaged by a wayward hoe. If the weather is exceptionally dry then do water but otherwise avoid it.

Once the bulbs start to mature the tops begin to yellow and eventually topple over. Leave the bulbs until this happens and during settled weather lift them with a fork leaving them on the surface for a couple of days to dry. The bulbs can then be stored in a dry shed or garage in net bags or seed trays or even tied into ropes.