How to Sow and Grow Leeks: A Complete Guide
Leeks are dependable, cold-tolerant alliums that occupy the ground for many months and provide valuable autumn and winter harvests. They are normally sown in a nursery area or modules, then transplanted once the stems are pencil thick.
Choosing leek varieties
Early leeks mature from late summer, while hardy maincrop types stand through winter. Choose varieties for the harvest window rather than sowing one cultivar for the entire year. Blue-green winter leeks are generally shorter and tougher; long white-shanked types often need more careful earthing up.
When and how to sow
Sow from late winter to mid-spring. Use deep modules, pots or a sheltered seedbed. Sow about 1 cm deep in peat-free seed compost, keep moist and provide bright light. Thin crowded seedlings so each develops a sturdy stem. Later sowings often remain too small before winter.
Preparing the ground
Choose an open bed with fertile, moisture-retentive soil that drains in winter. Add mature compost before planting. Leeks tolerate heavier soil better than onions but dislike stagnant water. Remove perennial weeds because hoeing between mature plants becomes difficult.
Transplanting leeks
When seedlings are roughly 15–20 cm tall and pencil thick, harden them off. Make holes 15–20 cm deep with a dibber, spacing plants 15 cm apart and rows 30 cm apart. Drop one seedling into each hole and water it in without filling the hole with soil; rain gradually washes soil around the roots.
Watering, feeding and blanching
Water after transplanting and during prolonged drought. A balanced organic feed or compost mulch supports steady growth. Draw soil around stems gradually if longer white shanks are wanted, but keep soil out of the leaf folds. Cardboard collars can extend blanching without heavy earthing.
Winter care
Hardy leeks can remain in the soil until needed. In regions with deeply frozen ground, lift a supply before severe weather or mulch the bed. Good spacing and airflow reduce rust and rotting during wet winters.
Common problems
Leek moth: cover crops with fine insect-proof mesh during local flight periods and remove mined leaves
Allium leaf miner: use mesh and dispose of infested plants safely rather than composting them
Rust: space plants well, avoid excess nitrogen and remove heavily affected foliage
White rot: remove plants and contaminated soil and rotate alliums away from the area for many years
Thin stems: sow early enough, prevent crowding and maintain moisture after transplanting
Harvesting and storing
Lift leeks once they reach a useful thickness. Loosen soil with a fork rather than pulling hard and damaging the shank. Harvest from autumn through winter according to variety. Leeks keep best standing in the ground; cleaned stems can be refrigerated, frozen after blanching or cooked into preserves and soups.
A reliable approach
Sow early, give seedlings room, transplant deeply and maintain steady growth through summer. Combining early and winter varieties provides a much longer harvest than relying on one sowing.
