🟢 Kohlrabi

Kohlrabi looks like an alien: a swollen, bulb-shaped stem that grows above the ground, with the flavour of a sweet, mild turnip crossed with broccoli stalk. It is one of the quickest and least troublesome brassicas, and gives fresh crisp crops from early summer through autumn.

It is ideal for small plots, as it grows fast, takes up little room and is often untroubled by pigeons and caterpillars. The stems are best eaten young, at tennis-ball size, before they become woody.

Varieties to try

Kolibri (purple, F1, reliable)Lanro (green, reliable)Superschmelz (grows large without turning woody)Adriana (white, tender)Azur Star (purple skin, quick)

Sow thinly outdoors from March to August in shallow drills 1–2 cm deep, in rows 30 cm apart, in fertile, moisture-retentive soil in sun or light shade. Sow a short row every two or three weeks for a continuous supply. March sowings under fleece or cloche are possible for an early crop.

Thin seedlings to 15–20 cm apart once they have a few true leaves. Kohlrabi can also be started in modules and transplanted at 3–4 weeks, taking care not to bury the stem. Late sowings in August give crops in October and November.

Top tips

• Sow short rows every two or three weeks.
• Thin early to give each plant room.
• Use fleece in early spring.
• Do not bury the swelling stem when transplanting.

Keep the plants growing steadily: water regularly, as slow or stressed growth leads to woody, fibrous stems, and mulch to keep the soil cool and moist. Hoe between plants carefully because the roots are shallow. They rarely need feeding in fertile soil.

Flea beetle on young seedlings can be prevented by fine mesh or by keeping the soil moist. Cabbage root fly, caterpillars and clubroot may also appear, as with other brassicas. Rotate with other brassicas, and lime acid soils.

Top tips

• Water evenly for tender stems.
• Use fine mesh against flea beetle.
• Mulch to keep soil cool and moist.
• Rotate with other brassicas.

Watch out for

Flea beetleCabbage root flyClubrootCaterpillars

Harvest kohlrabi when the stems are about the size of a golf ball to a tennis ball, around 5–7 cm across, usually 8–10 weeks after sowing. Larger ones can turn woody and fibrous, apart from giant varieties such as Superschmelz. Pull or cut at the base with a knife.

Pick regularly as plants ripen, because the swollen stems can quickly become tough in warm weather. Cut off the leaves, which are edible and can be cooked like cabbage. Late-sown crops can stand in the ground into November.

Top tips

• Pick at golf-ball to tennis-ball size.
• Harvest regularly; they toughen quickly.
• Eat the young leaves as greens.
• Lift late crops before hard frosts.

Peel off the tough skin and eat kohlrabi raw, grated into slaws or sliced thinly with lemon and salt for a crunchy snack. It can also be steamed, roasted, stir-fried, mashed or added to soups and curries, where it tastes like a sweet turnip. Young leaves can be sautéed like spring greens.

Trimmed stems keep for two to three weeks in the fridge in a bag. Peeled, cubed kohlrabi can be blanched for two minutes and frozen. Do not wash until needed, and keep it away from strong-smelling foods.

Top tips

• Peel thickly, as the skin is tough.
• Slice thinly raw with lemon, salt and olive oil.
• Roast cubes at 200°C until golden.
• Cook the young leaves like cabbage.