Leeks (Allium ampeloprasum Porrum group) are a vegetable that have been enjoyed a long time, back to 2000BC. The leek is also the national emblem of Wales. Provided you’ve a cool climate garden, it can be grown to maturity over a few cooler months.
Leeks are flavorful, nutritious and easier to digest than their onion cousins. They’re also easy to grow, tolerant of cold weather – and very expensive to buy in the supermarket. What more reason could you need to add a big patch of them to your kitchen garden?
Ensure that your garden will provide the right temperature range. Leeks need a temperature range from 13-24ºC. If you have a mild climate, leeks can be grown all year round.
Prepare the soil. The perfect soil for growing leeks is a near-neutral clay loam soil. Dig in a lot of organic matter before planting and prepare to soil down one spade length. Leeks will grow well in a range of soils, provided that they're given enough manure.
Sow the seed. The best time to sow leek seed is from spring into late summer or early autumn. While it is fine to plant direct in the garden, most gardeners prefer to plant out seedlings either home grown or purchased from the nursery. Seedlings are best transplanted when they're about 12-20cm in height.
Plant to ensure stem blanching (white stems): Make trenches in rows. The rows should be 45-50cm apart. Plant each seedling 15-20cm in the trench. Infill the trenches as the leeks grow so that the "stems" of the leeks get covered in soil. Another method is to plant the seed deep, about 10cm. This will help the white shank to develop.
Water well. Be generous with regular watering unless there is sufficient rain. Mulch lightly to help retain moisture.
Fertilise generously. A homemade source of fertiliser is fine. Manure is a good for fertilising leeks. The slow release of nitrogen provided by leeks is very helpful for their lush growth.
Harvest. The leeks can be harvested young or full grown, depending on your culinary needs. The growing season is a long one, about 16 to 30 weeks. The more mature leeks can be left in the ground until they're needed if it's autumn or winter. When the stems are 2.5cm they're ready for harvesting unless you're looking for more tender younger ones. Cease keeping them in the ground once they start to flower.