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Onions and shallots
Onions are one of the most versatile vegetables and are pretty easy to grow. Most people grow from sets - immature bulbs - although seed is available for onions; shallots are always grown from sets.
Sets are quicker to mature, are better in colder regions, less likely to be attacked by some pests and diseases and need less skill to grow; it is always worth buying heat-treated sets.
Sowing/Planting
Plant onion sets 10cm (4in) apart in rows 10cm (8in) apart from mid-March to mid-April. Plant shallots 15cm (6in) apart in rows 23cm (9in) apart from mid-February to mid-March. Gently push the sets into soft, well-worked soil so that the tip is just showing and firm the soil around them. Birds can be a problem lifting the sets so carefully remove the loose skin at the top of the set before planting.
Sow seed 13mm (0.5in) deep in rows 20cm (8in) apart from late February through to early April. Thin first to 5cm (2in) apart and then again to 10cm (4in) apart.
Growing
Water if the weather is dry and give an occasional feed with a general liquid fertiliser. A light feed of sulphate of potash in June will help ripen the bulbs ready for storage.
Mulching the soil will help conserve soil moisture and keep down weeds. Stop watering and feeding once the onions have swollen and remove any mulch or soil to expose the bulb to the sun.
Remove any flower spikes as soon as they are seen.
Harvesting
Onions can be harvested when the foliage turns yellow and starts to topple over. Although it is sometimes suggested to bend over the foliage or gently lift the bulbs to break the roots this is no longer recommended. Leave for two to three weeks and then carefully lift with a garden fork. Those for storage must be firm, disease free and then dried for two to three weeks, either laid out in the sun or in a shed if the weather is wet.
The foliage of shallots will start to turn yellow in July. Lift the bulb clusters, separate them and allow to dry.
Cultivars
View the AGM list (356KB pdf document)
