Growing Leeks and onions like a long growing season. Seeds need to be sown as early as possible for large specimens, and can be sown from January indoors, in trays or modules, and from February to April outside, in rows 20cm apart and 1cm deep.
The soil should be well firmed after sowing. Keep the seedlings well weeded and when large enough to handle transplant into a well fertilised bed. Leek seedlings should be dropped into a hole 2cm in diameter and about 10cm deep, watered in and left without filling the hole. The holes should be at least 20cm apart.
The more space you give them when planting out or thinning the bigger they will be. Leeks and onions do not compete well with weeds, and need to be kept very clean, but hoe carefully so as not to get soil inside the leave of the plants.
Onions should be harvested when the leaves start to dry and fall over. They need to be thoroughly dried in a green house or sunny windowsill to keep well. Leeks will last all winter in the garden so harvest as needed from September on.