Kohlrabi

Kohlrabi is a biennial brassica grown as an annual, producing a swollen, globe-shaped stem that sits above the soil. Flesh is crisp, sweet, and mild — comparable to broccoli stem or a mild turnip. It thrives in cool conditions with consistent moisture and tolerates light frost, making it well suited to both early and late growing periods. Both white and purple-skinned varieties are available; the leaves are also edible and used like kale.

Growing

Sow seeds 1 cm deep once soil is workable and warming. For an early harvest, sow indoors in trays 4–6 weeks before transplanting outdoors, using individual cells to minimise root disturbance. Seeds germinate best at around 20 °C but tolerate cooler soil from about 5 °C. Thin or transplant to 10–20 cm apart within rows, with rows 35–50 cm apart. Direct sow in succession outdoors once soil has warmed. Avoid transplanting in warm spells that may trigger premature bolting.

Care

Water consistently — uneven moisture causes woody texture and cracking. Apply a balanced fertiliser at planting and a nitrogen-rich feed once bulbing begins. Use row covers or fine mesh to protect against cabbage white butterflies and slugs. Keep beds weed-free, especially during early growth. No staking required. Top-dress with compost mulch to retain soil moisture and moderate temperature fluctuations.

Harvest

Harvest when the swollen stem reaches 5–8 cm in diameter for standard varieties; large-bulbing types (such as 'Superschmelz') can be left to 20 cm or more without becoming woody. Firmness and smooth skin indicate prime eating quality. Cut the stem at soil level with a sharp knife. Harvest before the flesh develops fibrous strands — a slight lift of the skin when pressed is a warning sign. Leaves can be harvested separately throughout growth.

In the kitchen

Eat raw, sliced thin in salads and slaws, or peel and grate as a crunchy base. Roast wedges at high heat to caramelise the natural sugars. Steam or stir-fry cubes as a side vegetable. Purée into soups with potato and leek. The leaves can be blanched or sautéed exactly like kale. Pairs well with apple, carrot, mustard, and yoghurt-based dressings.

Storing

Store unwashed bulbs in the refrigerator crisper drawer for up to 2 weeks. Large, firm varieties keep for several months in a cold, humid cellar (0–4 °C, 90–95% relative humidity). Remove leaves before long-term storage to prevent moisture loss from the bulb. Do not freeze raw; blanch cubes for 2 minutes before freezing for up to 3 months.