How to Grow Onions

Onions grown from seed include those used for salads and garnishes – known as spring onions, scallions or ‘shallots’ – and for pickling, as well as Welsh onions and the three common main crop groups of globe onion:

Welsh, Japanese or ciboule onion- Not to be confused with leeks, this is a hardy, long-lived perennial that forms a clump of plants by dividing at the base. It is propagated by division or seed sown in spring.

Early autumn-sown globe onions- Sow seeds in early autumn. In cool climates sow under glass; transplant seedlings to the permanent bed in spring. In warm climates sow directly into the ground. Pull and store bulbs in the second half of summer.

Late autumn to early winter-sown globe onions- For a crop the following autumn, sow seeds in late autumn to early winter. In cool climates sow under glass and transplant bulblets to the permanent bed in spring. In warm climates sow directly in the ground.

Spring-sown globe onions- In spring, sow seeds directly in the ground for a crop that will be harvested in autumn. Onion sets are immature bulbs ripened the previous summer. They can be planted in spring to produce an autumn crop, which ripens at the same time as winter-sown varieties. Onion sets are sold by some seed merchants or can be raised from seed.

Planning the crop
Onions need a site in full sun, and do best on a light, deep loam. Soil must be well manured; dig the plot deeply and work in two buckets of well-rotted manure or compost per square metre. Onions of all types grow best in firm ground, so prepare the bed well in advance to give it a chance to settle. Two weeks before planting, apply a dressing of 120 g of bonemeal and 60 g of sulphate of potash per square metre. Or rake in 90 g pelleted slow-release organic fertiliser just before planting. Onions are very sensitive to highly acid soils. A pH between 6.2 and 7.0 is ideal; rake in lime or dolomite if needed. Onion seed requires a minimum temperature of 5°C to germinate.

How many to grow- A 9 m x 1 m bed should produce about 100 onions weighing at least 12 kg. But good feeding and care can double yield, whether growing from seeds or sets. If sown in succession, rows of spring onions only 1 m long should keep a family supplied. A 3 m row of pickling onions will yield 100 to 150 onions.

Varieties

Welsh, Japanese or ciboule

Beltsville Bunching- Widely adapted; tolerates hot, dry conditions.

Ciboule Commune Rouge- Strong flavour; very hardy; ideal for soups.

Tokyo Long White- Only one to two stems but exceptionally tender.

Kujo Green- About four stems; much used in stir-fries.

Globe onions

Alisa Craig- Gold-skinned, very large bulbs with firm, sweet flesh; longkeeping; plant spring and autumn; ideal in cool climates.

Australian Brown- A superb keeper; medium, somewhat flattened, bulbs with pungent, pale yellow, firm flesh.

Bedfordshire Champion- For cool climates; large pale brown-skinned bulbs with medium–hot, firm flesh; susceptible to downy mildew.

Kelsea Sweet Giant- A huge, show winning variety with mild, sweet flesh; excellent keeper.