Leek
Allium ampeloprasum
Leeks are one of the most valuable winter allotment crops, standing in the ground from October through to April and shrugging off frost, snow, and everything British weather throws at them. They have a subtle, sweet onion flavour and silky texture when cooked. Sow seeds thinly under cover in March, then transplant in June when the seedlings are pencil-thick. The traditional planting method is to make holes 15cm deep with a dibber, drop a seedling in, and simply water — don't fill the hole with soil. As the leek grows, the blanched white stem develops naturally. For longer white stems, earth up around the plants as they grow. 'Musselburgh' is the classic hardy variety; 'King Richard' is an early type ready from September. Leeks have few pest problems, though leek moth is increasing in parts of the UK — fine mesh provides protection.
When to Sow Leek
Sow leek in March, April.
Time to Harvest Leek
Expect to harvest approximately 7 months after sowing, usually from September to April.
Companion Plants for Leek
- Nantes Carrot
The classic pairing: leek scent is thought to confuse carrot fly, and carrot scent may deter leek moth and onion fly.
- Celery
Leeks and celery are traditionally grown together; both need deep, rich soil and plenty of water.
Avoid growing leek near
- Broad beans: Alliums and beans are traditionally kept apart, as the beans are said to grow less well beside onion-family crops.
- Peas: Peas are traditionally kept away from the onion family, as they are said to be checked by growing alongside.
Expected Yield
Each plant produces one leek; expect 3–4kg per metre of row.
Common Problems with Leek
Leek rust
Orange pustules appear on the leaves, typically in warm, humid conditions from late summer onwards. While unsightly, leek rust rarely affects the usable white stem beneath. Remove the worst-affected outer leaves, improve air circulation by spacing plants generously, and avoid high-nitrogen feeds which produce soft, susceptible growth. Most leeks are still perfectly edible despite some rust damage.
Leek moth
Small caterpillars bore into the stems and leaves, creating tunnels that allow secondary infections to enter. Leek moth has two generations per year (May–June and September–October). Cover plants with fine insect-proof mesh during these peak risk periods. Check stems regularly for entry holes and frass (droppings), and remove any severely damaged plants.
Allium leaf miner
A relatively new pest in the UK whose larvae mine through leaves and into the stem, causing distorted growth and creating entry points for bacterial rot. Cover with fine mesh during the two main egg-laying periods: March–April and October–November. There are no approved chemical controls — physical barriers are the only reliable protection.
Leek: common questions
When should I sow leek in the UK?
Sow leek from March to April. Sow under cover (a greenhouse, windowsill or heated propagator) and plant out once the weather has warmed.
How far apart should I plant leek?
Space leek about 15cm apart. It grows to around 75cm tall. Sow seeds 1cm deep.
How long does leek take to germinate?
Leek seeds usually germinate in 14–18 days, depending on temperature.
When is leek ready to harvest?
In the UK, leek is usually harvested from September to April. It's ready about 7 months after sowing.
Does leek come back every year?
No. Leek is a biennial that's grown for a single season: it's harvested in its first year, before it would flower, so sow it fresh each year.
What grows well with leek?
Good companions for leek include Nantes Carrot and Celery. See the companion plants section above for why each one helps.
What should I not plant near leek?
Avoid broad beans: alliums and beans are traditionally kept apart, as the beans are said to grow less well beside onion-family crops. Avoid peas: peas are traditionally kept away from the onion family, as they are said to be checked by growing alongside.
Is leek frost hardy?
Yes. Leek is hardy and survives a normal UK winter outdoors.
What crop rotation group is leek in?
Leek belongs in the alliums group for crop rotation. Grow it in a different bed each year, alongside other alliums, so pests and diseases don't build up in the soil.
Leek guides
Plan your leek in the allotment planner
Drag and drop plants onto your plot and get personalised sowing reminders.
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