Sow seed from April to July in a sunny position. Sow seed thinly, 13mm (0.5in) deep, in rows 30-38cm (12-15in) apart; the wider distance is best for semi-mature to full-size heads.
Earlier and later sowings for baby leaf can also be made under cloches or fleece in mild areas.
Gradually thin seedlings to 7.5-10cm (3-4in) for baby leaf, to 20cm (8in) for semi-mature plants and to 25-30cm (10-12in) for mature plants. The thinnings can be eaten.
Keep plants well watered throughout the growing period to avoid bolting (running to seed) and lack of flavour.
Harvest as and when needed.
'Joi Choi': Is slow to bolt and has good frost resistance.
'Canton Dwarf': Is compact with dark green leaves.
Flea beetle: Leaves are peppered with small holes, damaged areas turn brown. Seedlings are particularly susceptible.
Remedy: Grow under horticultural fleece, keep the soil moist.
Read more on on flea beetle
Powdery mildew: A white powdery deposit appears over the leaf surface, leaves become stunted and shrivel.
Remedy: Keep the soil moist, grow in cool locations, spray using plant and fish oils or sulphur based controls.
Read more on powdery mildew
Bolting: Plants flower and set seed, rather than producing edible roots. This is usually caused by stress usually drought.
Remedy: Sow bolting resistant varieties, warm the soil before sowing early crops, grow under the protection of fleece or cloches and keep the soil moist.