Create a firm seed bed in any reasonably light, fertile, free draining soil.
Sow seeds, 13mm (1/2in) deep in rows 30cm (12in) apart from late February (undr cloches or fleece) to early March, continuing until mid-August in warmer areas.
Sow a little and often, say every three weeks, for a constant supply.
In cooler areas and where soil is heavy clay, early crops can be sown in modules, hardened off and transplanted when the soil warms up, when they a maximum of 5cm (2in) high.
Transplant seedlings sown in modules in March.
Thin out seedlings when they are 2.5cm (1in) tall or the first true leaves appear, leaving a final spacing of 15cm (6in) apart.
Keep the soil constantly moist and weed free, watering before the onset of drought.
Net or fleece young plants, to protect against birds and cabbage rootfly.
It's important to harvest when the plants are young and the swollen stem bases are between golf- and tennis ball-size. If you leave them too long they lose their taste and tenderness.
Plants can be harvested until mid-December.
The leaves can also be eaten.
‘Superschmelz’: A mild, sweet tasting white cultivar, remains tender whatever the size.
‘Blusta’: Fast maturing and resistant to bolting.
‘Domino’ AGM: An early variety, good for growing under cover.
‘Kongo’ AGM: Top quality, fast growing, sweet, juicy and high yielding.
Cabbage root fly: Problem: White larvae approximately 5cm (2”)long, feed on the roots just below the soil surface, stunting growth; plants may wilt and die.
Remedy: Grow under horticultural fleece or insect proof mesh or put 12cm(4.5in) collars or cardboard, plastic or similar around the base of the plants – transplants and seedlings are most vulnerable.
More information on cabbage root fly
Flea beetle: Problem: Leaves are peppered with small holes, damaged areas turn brown. Seedlings are particularly susceptible
Remedy: Grow under horticultural fleece, keep the soil moist.
More information on flea beetle
Club root: Problem: Roots become swollen and distorted, leaves become pale and yellow and wilt easily. Plants may die.
Remedy: Improve drainage, lime to make soil more alkaline, remove and burn all infected plants immediately. Avoid moving soil around on your boots and tools. Grow your own plants or buy from a reputable source. Do not grow kohl rabi in affected soil.
More information on club root