Sow thinly 13mm (0.5in) deep in rows 15cm (6in) apart in a seedbed in March and April.
Thin out seedlings to approximately 4-5cm (1.5-2in) apart.
The plants are ready to transplant in June when they are about 20cm (8in) high and the thickness of a pencil. Water well the day before lifting and transplanting. Prepare the plants by trimming off the root tips.
Make 15cm (6in) deep holes with a dibber 15cm (6in) apart in rows 30cm (12in) apart and drop a plant into each hole. Fill the hole with water to settle the roots. Top up with water as necessary for the plants to establish. If you have a lot of plants, try dropping two or three into each planting hole. You'll get smaller leeks but the overall yield should be the same.
To increase the length of white stem it can be blanched by gently drawing up dry soil around the stem in stages, but try not to allow soil to fall between the leaves. An easier way to blanch the stems is to slide a section of drainpipe, cardboard or similar over the plants. Using this method, together with growing in fertile raised beds, means you can plant 23cm (9in) apart in all directions.
Start lifting when the leeks are still quite small to ensure a long harvest period. Gently lift from the soil using a fork.
Leeks can remain in the ground through the winter until they are needed.