Prepare the soil early, preferably over the winter. Dig over thoroughly, removing stones and weeds, forking in well-rotted manure to improve moisture retention. The soil can be heavy and the leeks will still grow well – however, ensure that drainage levels are maintained. One method of doing this is to mix in some horticultural sand.
A week before sowing, rake in a little general fertiliser. Plant rows 30 to 35 cm apart. Create a shallow groove or furrow around 1 cm deep and sow the seed thinly along this row.
Cover over the row with soil and gently water in well. In just over a month, seedlings will have grown up and started leafing – when they have three leaves, thin the plants down to 15 cm gaps. You can replant the thinned out seedlings elsewhere.
If you’re planting out plug plants, position each plant into individual holes (around 20 cm deep) in late May and water into each hole – do not fill the hole back in. Soil will be drawn over the roots while leaving space for the leek stems to grow. Keep the leeks watered well, and harvest from September on.