How to Grow Leeks in the UK

How to Grow Leeks in the UK: Complete Growing Guide

Leeks are one of the most rewarding winter vegetables for UK gardeners. Hardy, versatile, and available for harvest from late summer right through to spring, they fill the hungry gap when little else is growing. This guide covers everything you need to grow leeks successfully.

Not sure when to sow? See our When to Plant Leeks UK →

Quick Growing Facts

Sowing Time: January to April (indoors from January; outdoors from March)
Transplant Time: May to July
Harvest Time: August to April
Growing Time: 16-20 weeks from sowing to harvest
Difficulty: Easy to moderate
Position: Full sun, open site

When to Sow Leeks

Indoor sowing: January-March in trays or modules for the longest season
Outdoor seedbed: March-April once soil has warmed above 7°C
Transplant: May-July when seedlings are pencil-thick (15-20 cm tall)
Early varieties: Sow January-February for August-November harvest
Maincrop varieties: Sow February-March for November-April harvest

Soil Preparation

Soil type: Deep, fertile, well-drained soil
Add organic matter: Dig in well-rotted manure or compost in autumn
pH level: Neutral to slightly alkaline (pH 6.5-7.5)
Firm the soil: Tread and rake to a fine, firm tilth before transplanting
Avoid waterlogging: Leeks hate sitting in wet soil over winter

How to Sow Leeks

Indoor Sowing (recommended):

Use trays or modules: Fill with seed compost; sow 2-3 seeds per module or thinly in trays
Sowing depth: Cover seeds with 1 cm of compost
Temperature: Keep at 13-16°C; germination takes 14-21 days
Thin seedlings: Reduce to one per module when large enough to handle
Grow on: Keep in a cool, bright place until transplanting time

Outdoor Seedbed Sowing:

Sow thinly in drills 1 cm deep, 15 cm apart from March onwards
Thin seedlings to 5 cm apart once established
Transplant when pencil-thick, usually 10-12 weeks after sowing

💡 Top Tip: The Dibber Method

Make 15 cm deep holes with a dibber, 15-23 cm apart. Drop one seedling into each hole and water in — do not backfill with soil. The hole gradually fills as you water, naturally blanching the shank and producing the long white stem leeks are prized for.

Transplanting Leeks

When to transplant: May-July when seedlings are 15-20 cm tall and pencil-thick
Trim roots and leaves: Trim roots to 2-3 cm and leaves by one-third to reduce transplant stress
Make deep holes: Use a dibber to make holes 15 cm deep, 15-23 cm apart, in rows 30 cm apart
Drop in seedlings: Place one seedling per hole; do not backfill
Water in: Water each hole thoroughly; soil will gradually fill in naturally
Firm in: After a few days, gently firm soil around the base of each plant

Ongoing Care

Watering: Water regularly during dry spells, especially in the first few weeks after transplanting
Weeding: Keep weed-free; leeks are slow-growing and easily swamped
Earthing up: Draw soil up around the stems as plants grow to increase the length of blanched white shank
Feeding: Apply a balanced fertiliser or liquid feed monthly during the growing season
Frost protection: Maincrop varieties need no protection; early varieties may benefit from fleece in hard frosts

Common Problems

Leek rust: Orange pustules on leaves caused by a fungal disease. Remove affected leaves; improve air circulation. Avoid overhead watering.

Allium leaf miner: White maggots tunnel through leaves and stems. Cover with fine insect mesh from March to April and October to November when the fly is active.

Bolting: Leeks left in the ground too long in spring will run to seed. Harvest all remaining leeks by April.

Thin shanks: Usually caused by late sowing, overcrowding, or poor soil. Sow early, thin properly, and improve soil with organic matter.

Harvesting Leeks

Early varieties: Harvest from August to November when shanks are 2-3 cm thick
Maincrop varieties: Harvest from November through to April as needed
Lift with a fork: Loosen soil with a fork before pulling to avoid breaking the shank
Harvest as needed: Leeks can stand in the ground until required — no need to harvest all at once
Before bolting: Harvest all remaining leeks by April before the central stem hardens

Storage

In the ground: Best storage is leaving leeks in the ground until needed (maincrop varieties)
Refrigerator: Store harvested leeks unwashed in the fridge for up to 2 weeks
Freezing: Slice, blanch for 2 minutes, cool, then freeze for up to 6 months

Recommended Varieties

King Richard: Early, long slender shanks, harvest August-November
Musselburgh: Classic maincrop, thick shanks, very hardy, harvest November-March
Bandit: AGM, late maincrop, outstanding frost resistance, harvest December-April
Oarsman: AGM, mid-season, long clean shanks, good disease resistance
Megaton: F1 hybrid, very uniform, heavy yields, good for exhibition