Choose an open, sunny site with good drainage which has preferably been dug and manured in the previous autumn. Do not plant or sow on freshly manured bed. Lime if the soil is acid. Avoid planting in an area where the previous crop was of the onion family. Many exhibitors grow their show onions in a permanent bed in order to build up fertility, but in the kitchen plot it is a much better idea to change the site annually.
Apply a general fertiliser if needed and rake the surface when the soil is reasonably dry. Tread over the area and then rake again to produce a fine, even tilth.
Sow in Autumn or Late Winter to Spring
Seeds can be sown direct in autumn to be harvested in 46 weeks to produce large bulbs (not advisable in very cold areas) Otherwise sow in February under cloches or direct March to April and harvest in 24 weeks. In cold areas and for exhibition bulbs sow under glass in January, harden off in March and transplant outdoors in April.
Sow very thinly in 1.2cm (½in) deep drills, leaving about 25 to 30 cm (10 to 12in) between rows. Water very gently if the soil is dry, and cover with soil.
When large enough to handle, thin the crop in two stages. Close spacing will give smaller onions than wider spacings. Lift the seedlings carefully – the soil should be moist and all thinnings removed to deter onion fly. (They may be used as spring onions)
Thin spring-sown seedlings first to 2.5cm (1in) then when the seedlings have straightened up to 5 to 10 cm (2 to 4in) apart.
Thin Autumn sown onion seedlings to about 2.5cm (1 inch) in the autumn. Further thin to about 5 to 10 cm (2 to 4 in) between plants in the Spring.
Seedlings raised under glass should be transplanted 4in (10cm) apart, leaving 9in (23cm) between the rows. The roots must fall vertically in the planting hole and the bulb base should be about 1cm (½in) below the surface. Plant firmly.
Hoe carefully or weed by hand – dense weed growth will seriously affect yield. Water if the weather is dry (not otherwise) and feed occasionally. Feed an autumn-sown crop in March. Mulching is useful for cutting down the need for water and for suppressing weeds. Break off any flower stems which appear. Stop watering once the onions have swollen and pull back the covering earth or mulch to expose the bulb surface to the sun.
When the bulb is mature the foliage turns yellow and topples over. (Some gardeners bend over the tops as the leaves start to yellow). Leave them for about 2 weeks and then carefully lift with a fork on a dry day.
Inspect the bulbs carefully – all damaged, soft, spotted and thick-necked onions should be set aside for kitchen use or freezing. The rest can be stored.
The onions which are not for immediate use must be thoroughly dried. Spread out the bulbs on sacking or in trays – outdoors if the weather is warm and sunny.
Drying will take 7 to 21 days, depending on the size of the bulbs and the air temperature..
Store in trays, net bags, tights or tie to a length of cord as onion ropes.
Choose a cool and well-lit place; they will keep until late spring