Leek

Leeks are a hardy and reliable vegetable to grow in the UK, valued for their mild onion flavour and versatility in soups, roasts, and winter dishes. They offer an impressively long harvesting period, often standing strong through frost and snow. With the right preparation and steady care, leeks grow well in most gardens, raised beds, and allotments, making them a rewarding crop for both beginners and seasoned growers.

Types and Timing

Leeks come in varieties suited to different seasons and purposes:

Varieties:

• Early varieties: Fast-growing types like ‘Summer Breeze’ for harvesting from late summer.

• Autumn varieties: Reliable mid-season options such as ‘Autumn Giant’.

• Winter-hardy varieties: Tough cultivars like ‘Blue Solaise’ and ‘Bandit’ ideal for cold-weather harvesting.

• Baby leeks: Many varieties can be harvested young for slimmer, sweeter stems.

Timing:

• Sow indoors from January to March.

• Sow outdoors from March to April.

• Plant out seedlings from May to June once they’re pencil-thick.

• Harvest window: August through to the following March depending on variety.

Site and Soil Requirements

Leeks aren’t fussy but perform best in well-prepared ground:

• Light: Prefers full sun but tolerates light shade.

• Soil: Fertile, moisture-retentive, and well-drained. Add compost months beforehand for best results.

• pH: Neutral to slightly alkaline soils are ideal.

• Containers: Can grow in deep containers or troughs, though best performance comes from open soil.

Propagation & Planting

• Sowing indoors: Sow thinly in pots or trays 1–1.5 cm deep. Keep lightly watered and transplant when seedlings reach pencil thickness.

• Direct sowing: Sow in shallow drills outdoors, then thin gradually as seedlings grow.

• Planting out: Create deep holes 15–20 cm apart in rows 30–40 cm apart. Drop seedlings into the hole without filling in soil—simply water in to settle; soil will fill naturally as plants grow.

• Trimming: Some growers trim roots and tops before planting out to encourage sturdy growth.

• Succession planning: Grow a mix of early, autumn and winter varieties to extend harvest through the year.

Growing & Maintenance

• Watering: Keep soil consistently moist, especially during dry spells—leeks need steady moisture for tender stems.

• Feeding: Apply a balanced fertiliser mid-season, especially in poorer soils.

• Weeding: Keep beds clear, as leeks dislike competition from weeds.

• Earthing up: As stems grow, draw soil around the base to blanch and lengthen the white portion.

• Mulching: Helps retain moisture and maintain even soil temperature.

Harvest and Post-Harvest

• Timing: Begin harvesting early varieties from late summer; winter types can be left in the ground and lifted as needed.

• Method: Use a fork to gently lift plants to avoid snapping stems.

• Harvest window: August to March depending on variety.

• Storage: Leeks store best in the ground, but can also be kept in a cool shed with roots wrapped in damp sand for several weeks.

• Cooking: Ideal for soups, pies, roasting, and braising. Young leeks can be eaten raw when very tender.

Troubleshooting & Pests

• Bolting: More common in stressed or overheated plants—sow at the right time and keep watering consistent.

• Splitting stems: Usually caused by erratic watering or rapid growth after drought.

• Pests:

  • Leek moth: Causes internal tunnelling - use insect mesh from spring onwards.

  • Allium leaf miner: Increasingly common in the UK - cover with fine mesh to prevent egg-laying.

  • Slugs: Target young seedlings; protect with barriers and traps.

• Yellowing leaves: Often a sign of nutrient deficiency - apply a general feed.

Tips from Growers / FAQs

• Best beginners’ option: Autumn varieties like ‘Autumn Giant’ are very reliable.

• Longer white stems: Earth up regularly or use collars around the stems.

• Winter supply: Plant hardy cultivars to enjoy veg even in freezing weather.

• Baby leeks: Sow thickly and pull young plants early for tender, slim leeks.

• Continuous harvest: Grow a combination of early, autumn, and winter varieties for season-long picking.

Resources & References

• RHS: Grow Your Own Leeks

• BBC Gardeners’ World: How to Grow Leeks