Kohlrabi

1. 1

   Pick variety by colour

   Azur Star: purple skin, white flesh, looks dramatic in the kitchen garden. Mild sweet flavour. The popular UK choice. Korist: green-skinned, slightly larger, very reliable — the green standard. Olivia: green-skinned modern variety, good bolt resistance. Superschmelz: massive heritage variety (can reach 8 kg!) — but stays tender even at large size. For the curious gardener. For a first crop: Azur Star purple — visual interest plus reliable mild flavour.

2. 2

   Sow direct, April to August

   Spring sowings (April–June): crop in summer. Late-summer sowings (July–August): crop in autumn–winter. Direct-sow in shallow drills 1 cm deep, 30 cm between rows. Germination in 7–14 days. Kohlrabi doesn't transplant well as mature seedlings (taproot disturbance triggers premature bolting); sow direct or use modules and plant out very young.

3. 3

   Thin to 20–25 cm apart

   Once seedlings have 3–4 leaves, thin to one plant every 20–25 cm. Don't crowd — overcrowded kohlrabi produces small globes. Use the thinnings in salads (very young leaves and small stems).

4. 4

   Water consistently for tender globes

   The single most important husbandry rule. Kohlrabi grown in dry conditions develops tough, woody, hot-tasting globes. Water deeply once or twice a week in dry weather. Mulch with garden compost to conserve moisture. Consistent moisture is more important than total water volume — fluctuating wet/dry conditions cause splitting and woody texture.

5. 5

   Harvest when tennis-ball sized

   Pick when the globe is 7–10 cm diameter — tennis-ball size or slightly smaller. At this size: tender, sweet, mild. Bigger than 10–12 cm: globes get woody, fibrous, and develop the hot bitter flavour of overgrown turnips. Cut with a sharp knife just below the globe — the rest of the plant can stay in the ground briefly but won't regrow (the swollen stem is the whole crop).

6. 6

   Use the leaves too

   Kohlrabi leaves are edible — like a softer cabbage. Young leaves (from the centre of growing plants): salad or stir-fry. Older leaves (when harvesting the globe): chop and cook like spring greens, kale, or any other brassica leaf. Don't waste them — they're often as good a crop as the globe.

7. 7

   Watch for cabbage white and slugs

   Cabbage white butterfly: caterpillars on leaves April–September. Cover with insect mesh from sowing through the cropping window. Slugs: love kohlrabi seedlings. Apply wool pellets and nematodes; protect young plants with crushed eggshells or copper rings. Pigeons: occasionally eat seedlings; mesh covers exclude them.

8. 8

   Sow successionally for continuous supply

   A single kohlrabi sowing matures over 2–3 weeks then needs harvesting before the globes get woody. Sow a fresh row every 3 weeks from April to August for continuous supply. For winter use: an August sowing gives autumn cropping (October–November) and the plants survive mild winters; in cold gardens, harvest before December and store in a cool shed (lasts 2–3 months wrapped in newspaper).

Cabbage white caterpillars and flea beetle are the main threats; less prone than cabbage.