All kohlrabi crops grow best in partial-shade, in firm, fertile, free-draining soil. Start digging over your soil in autumn, removing any stones you find and working in plenty of well-rotted manure or compost. Tread on the soil to remove any air pockets and make the surface very firm. Nearly all kohlrabi should be planted in a fowerbed or in modules under glass and then transferred. Seeds should be sown thinly, as this reduces the amount of future thinning necessary and potential risk from pests. Sow seeds 1.25cm (1/2in) deep and rows should be spaced 15cm (6in) apart. Once the seeds have germinated, thin the seedlings to 7.5cm (3in) between each plant.
Cabbage and broccoli seedlings are ready for shifting when they are between 6 and 8cm high (2.5-3in). Brussels sprouts and kale should be 15cm (6in). Water the day before moving, and keep well-watered until established. Space the plants according to the instructions on the seed packet. It can vary from 30cm for small cabbages to 75cm for Brussels sprouts.