Leeks prefer a sunny, sheltered site with well-drained soil. As they will sit in the soil for a long time, they are ideal crop for the allotment, although many have fantastic foliage that makes them an ideal vegetable to grow in flower borders or an ornamental potager.
If possible, prepare the soil for planting in the winter. Dig the site well, removing weeds and working in plenty of well-rotted manure to improve its ability to retain water. Leeks can be planted in heavy soil, but improve the drainage by mixing in some horticultural sand. This is a hungry crop – spread a general balanced fertiliser over the soil a week or so before sowing and rake in. A rate of 60g per square metre is ideal.
The easiest method is to sow seed directly into the soil between March and April. Alternatively, you could cheat and buy ready-grown seedlings, many nurseries offer a good range. By careful choice of varieties you could have an ample supply of leeks to harvest from mid-summer until the following spring.
On the allotment seeds are best sown in rows, 30cm apart. Mark a straight line and use the corner of a rake to make a shallow groove in the soil, about 1cm deep. Sow seed thinly along the trench, cover with soil, water and label. When seedlings have three leaves each, about four to five weeks later, thin to leave plants every 15cm – the seedlings you remove could be used to plug gaps elsewhere.