Sow thinly in pre-watered, shallow, short rows, lightly covering the seeds with soil. Keep the seedbed moist at all times. Plant out when plants are about 15cm/6in high. Allow 20cm/8in between plants and 45cm/18in between rows. Make holes with a dibber about 15cm/6in deep, and drop a plant into each hole. Fill each hole with water, but not with soil. To ensure a long white shaft, draw up soil round the plants as they develop.
Leeks do best in an open position on rich, well-worked soil into which plenty of well-rotted organic matter has been added. They have a high nitrogen requirement.