Chinese cabbage is an excellent crop for late summer when days are long and nights warm. At other seasons it bolts readily and is satisfactory only as mini leaves.
Sow in very fertile soil and water carefully to ensure good growth and to suppress bolting. Sow thinly outdoors from June to August, every three weeks for successional crops, 13mm (0.5in) deep in rows 38cm (15in) apart.
Thin seedlings to 30cm (12in) apart for large heads or to 15cm (7in) apart for ‘cut and come again’ salad leaves.
Chinese cabbage needs a deep, moisture-retentive soil and a firm bed on an open sunny site; it benefits from some shade in summer. Add manure and fertiliser before sowing.
Acidic soils should be limed if necessary as this crop is very susceptible to clubroot disease – a fungal organism suppressed by alkaline conditions.
Water before the onset of drought, to keep the soil moist and prevent ‘bolting’.
Keep soil weed free.
Harvest ‘cut and come again’ crops, from seedlings to semi-mature plants, using scissors or a sharp knife. Plants that are harvested once the root has established will re-sprout several times then finally ‘bolt’. When this happens, harvest the flower heads before they start to open, as you would broccoli.
Most cultivars form hearts well, but some might need binding. Tie up the heads of hearting varieties with soft twine or raffia when they reach maturity. Protect maturing plants with cloches, from autumn onwards, to stop moisture from rotting the heart.
Mature heads can be cut and stored in a frost-free shed or refrigerator. Remove the head and leave the stump to produce more, smaller heads or ‘cut and come again’ leaves.
There are three main types of Chinese cabbage: tall cylindrical; hearted or barrel shaped; and loose headed. Tall cylindrical types can be loosely tied to blanch the inner leaves, hearted types have tightly wrapped leaves and loose leaved have a lax, open habit.
‘Early Jade Pagoda’ AGM: A cylinder-shaped or ‘Michihili’ type. Uniform, with dark-green outer leaves and a short internal stem. Late maturing.
‘Kasumi’ AGM: High yielding and barrel-shaped, with solid heads and pretty green outer leaves.
‘Questar’: Medium-large with dark green outer leaves and firm. Slow to bolt and can be harvested around 65 days from sowing; claims to be club-root resistant.
Slugs: Eat the leaves and young shoots.
Remedy: Non-chemical controls including watering in nematodes at sowing or planting use pellets based on ferric phosphate.
Read more information on slug control
Flea beetle: Leaves are peppered with small holes, damaged areas turn brown. Seedlings are particularly susceptible.
Remedy: Grow plants under horticultural fleece, keep the soil moist.
Read more information on flea beetle
Cabbage root fly: Female flies lay eggs around stems and the resulting larvae eat the roots; look out for wilting plants that produce reddish leaves.
Remedy: Grow plants through brassica collars – you can buy these, or make your own from discs of felt (7.5cm/3in) with a radial slit and position the discs on the soil at the base of the plant around the stem. You could also cover plants with fine netting, such as Enviromesh, which also prevents cabbage white butterfly and keeps pigeons at bay. Don’t grow cabbages in the same place as you grew them (or other brassicas) last year.
Read more information on cabbage root fly
Cabbage caterpillars: The most common of the caterpillars that eat the leaves of Chinese cabbage are those of cabbage white butterflies. You will usually see the caterpillars; if not, you will see the holes they make in the leaves. They will also bore into the heart of cabbages.
Remedy: In mild attacks, or if you have only a few plants, you may be able to pick the caterpillars off. You can spray with pyrethrum or bifenthrin. But the best way is to prevent the butterflies laying eggs in the first place by covering the cabbages with fine netting, such as Enviromesh.
Read more information on cabbage caterpillars
Club root: This is a fungal disease causing stunted growth, purplish foliage and wilting in hot weather. The root system also becomes swollen and distorted. It is worse on acidic soils and in warm, wet weather.
Remedy: If you have acidic soil you should apply lime before you plant. Test soil acidity using a pH meter which you can buy from DIY stores, or garden centres. If the pH of your soil is less than pH6, it is acidic. Once you see the symptoms of club root, there is very little you can do.
Read more information on club root