At a glance
Ease of Culture: Easy
Where: All zones
Best climate: Cool, and temperate
When to plant: Autumn and winter
Spacing: 10-20 cm
Harvest: Spring and summer (20-25 weeks)
• Leeks prefer cool to warm conditions in the range of 12-25°C
• In cold areas, they are best sown in spring to early autumn for transplanting later
• In warm areas, plant in early autumn and harvest late winter/spring
• Leeks grow in a wide range of soils but like a well-drained soil moderately rich in humus
• It is a good crop to plant following a crop that has been heavily manured like corn or lettuce.
• Use a garden fork to loosen the soil well, and then mound the soil to help improve drainage.
• Add lime if your soil is acidic.
Leeks grow best in full sun but will tolerate part shade
• Leeks are easy to grow from seed or seedlings.
• Seed are best sown into punnets for transplanting later.
• Fill punnets with a good quality seed raising mixture. Sprinkle seed on the surface and press the seed into the mixture to create close contact.
• Gently water seeds in and keep the mix moist until they germinate.
• Place punnets in a warm spot that gets a few hours of morning sun
• After germination, keep the mix evenly moist and feed with a liquid fertiliser once a week to encourage healthy growth and establishment.
• Seedlings are ready for planting out around 8 weeks after germination
While all parts of the leek are edible, it’s the sweet tender white section that is preferred for cooking. 'Blanching' - the process of denying the lower section of the stems of sunlight as they grow - helps to increase the white section. This is achieved by planting seedlings deeply and covering the lower stems with a short section of PVC pipe or milk carton as they mature.
• Dig planting trenches or rows 20cm deep and 20-30cm apart
• Separate and plant seedlings 10-20cm apart along the trench
• As the plants grow, gradually backfill the soil in the trench to cover and blanch the lower stems.
Watering and fertilising
• Water crops regularly to keep soil moist.
• Sprinkle a little organic fertiliser along the rows once every six weeks to keep plants developing strongly.
• Leeks can be harvested at an time you feel they are big enough to cook with
• The ideal size for harvesting is when their diameter is around 2.5 cm
• Aim for a blanched section at least 10-15cm long.
• Large mature leeks may require a garden fork to help lift them out of the ground.
• Leeks can be left in ground for extended periods without loss of quality – up to 12 months in cool to temperate climates (less in tropical and subtropical zones).
Pest and diseases
Leeks are largely pest and disease free. Thrips may attack the foliage, but they cause little damage to the crop. Snails and slugs will sometimes lodge themselves between the leaves – inspect the plants periodically and pick these out.
In the kitchen
The delicate mild flavour of leek can be enjoyed in soups, sauces, pies, tarts and casseroles and sautéed and served as a side dish. Leeks need to be washed and cleaned thoroughly before cooking to remove the soil that collects at the base of the leaves.