How to Grow Leeks

Overview

Leeks are a hardy, reliable winter vegetable that stand well in the ground and can be harvested from autumn through to spring. Their mild onion flavour makes them indispensable in soups, stews, and gratins. Leeks are less prone to pests and diseases than most alliums, making them a rewarding crop for any gardener.

Health Benefits

Excellent source of Vitamin K: Leeks are rich in Vitamin K, which is essential for healthy blood clotting and supporting strong bones.

Folate and prebiotic fibres: A good source of folate for cell health, and rich in prebiotic fibres that may help nourish beneficial gut bacteria and support digestive wellness.

Kaempferol antioxidant: Leeks contain kaempferol, a flavonoid antioxidant being studied for its potential anti-inflammatory benefits. Though milder than onions, leeks are equally nutritious.

Soil Preparation

Leeks prefer deep, fertile, well-drained soil that has been enriched with well-rotted compost or manure. A neutral to slightly acidic pH of 6.0 to 7.0 is ideal. Dig the soil deeply as leeks need to be planted in holes or trenches to blanch the stems. They are tolerant of heavier soils than most alliums.

Sowing & Planting

Sow seeds indoors from January to March in modules or trays at 13-16°C. Transplant from May to June when seedlings are pencil-thick, about 20cm tall. Make holes 15cm deep with a dibber, drop one leek into each hole, and water in without backfilling. Space 15cm apart in rows 30cm apart. The holes gradually fill with soil as you water.

Care & Maintenance

Water during dry spells and keep the bed weed-free. As the leeks grow, draw soil up around the stems to increase the length of blanched white shaft. Feed with a balanced fertiliser once or twice during the growing season. Leeks are generally trouble-free and need less attention than most brassicas.

Harvesting

Leeks are ready to harvest from September through to March, depending on variety. Ease them out with a fork rather than pulling, to avoid breaking the stems. They can be left in the ground and lifted as needed throughout winter, as they tolerate frost and cold extremely well.

Common Problems

Leek rust causes orange pustules on leaves. It is usually cosmetic rather than damaging. Improve spacing and air circulation and remove badly affected leaves.

Leek moth caterpillars mine into the leaves and stems. Cover with fine mesh from May onwards and check regularly.

Allium leaf miner causes white patches on leaves and pupae in the stems. Use insect-proof mesh covers in April-May and October-November.

Companion Planting

Leeks grow well alongside carrots and celery, with the strong allium scent helping to confuse carrot fly. Avoid planting near beans and peas, which alliums can inhibit.