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.
Flea beetle: Leaves are covered in small holes and damaged areas turn brown. Seedlings are particularly susceptible.
Remedy: Grow plants under horticultural fleece and keep the soil moist. Water in nitrogen-rich fertilser to help the crop outgrow the pest.
More info on Flea beetle
Powdery Mildew: Appears as a white powdery deposit over the leaf surface and leaves become stunted and shrivel.
Remedy: Keep the soil moist, grow in cool locations, and spray using plant and fish oils or sulphur-based controls.
More info on Powdery Mildew
Bolting: Plants flower and set seed, rather than producing edible roots. This is usually caused by stress – a cold spell or drought.
Remedy: Sow bolt-resistant varieties and keep the soil moist.
More info on Bolting
Harvest as and when needed.
'Joi Choi': Is slow to bolt and has good frost resistance.
'Canton Dwarf': Is compact with dark green leaves.