Growing Leek in a pot
For balcony, patio or terrace — Allium porrum
leek grows well in a pot of at least Ø 20 cm (6 L capacity), in a position with full sun. Watering: every 2 days in summer, once every 2 weeks in winter.

Which pot?
Ø 20 cm
~ 6 L potting soil
Give the plant room with a pot slightly wider than the current rootball, with matching depth.
Watering
every 2 days
once every 2 weeks
Always use a pot with drainage holes. Water dries out faster in pots — or the plant drowns. Check weekly with your finger: only water when the top 2 cm of soil is dry.
Pot care
Leeks need consistent moisture throughout the growing season, particularly from late spring through summer when they're putting on growth. Water regularly during dry spells to keep the soil evenly moist but not waterlogged. In clay or loam soils with good structure, once or twice a week is usually sufficient, but increase frequency during hot, dry weather. Reduce watering from autumn onward as growth slows and rainfall typically increases. Feed leeks in May and June with a balanced general-purpose fertiliser or a nitrogen-rich feed to promote strong leafy growth and thick stems. A liquid feed every two to three weeks during this period works well, or apply a granular fertiliser according to the packet instructions. Avoid feeding after midsummer, as leeks need to harden off before winter. Leeks are fully hardy across zones 4a to 10b and will stand in the ground through winter without protection, making them an invaluable fresh vegetable from autumn to early spring. In fact, many varieties improve in flavour after a frost. Mulch around the base with compost or straw in autumn to suppress weeds and retain moisture. Common pests include leek moth, whose larvae tunnel into the leaves and stems, and onion fly maggots, which damage roots. Cover crops with insect-proof mesh from May onward to prevent egg-laying. Rust (orange pustules on leaves) can be a problem in humid conditions—ensure good spacing for airflow and avoid overhead watering. Rotate your leek bed each year to reduce the build-up of soil-borne pests and diseases.
Pot-specific tip: add slow-release fertiliser pellets in March — potting soil exhausts much faster than open ground.