How to Grow Leeks
On this page
Leeks are ready to move from seed tray to garden once seedlings reach about 20cm tall and are pencil-thick — typically around eight weeks after an indoor sowing — and they germinate best once compost is kept above 10°C. They're also exceptionally frost-hardy: once transplanted, they can be left standing in the ground and lifted as needed rather than harvested all at once.
The short answer
- Site
- 6+ hours of sun, soil pH 6–6.5
- Biggest risk
- Allium white rot
Core growing advice on this page is checked against named horticultural sources — see References.
Leek (Allium ampeloprasum var. porrum)
14 sources cited · Verified
Quick Facts
| Factor | Value |
|---|---|
| Soil pH | 6 - 6.5 |
| Sunlight | 6-10 hours direct sun |
| Germination temp | 10°C |
| Optimal growing temp | 18-24°C |
| Minimum survivable temp | -5°C |
| Soil texture | RHS: improve soil by "digging in two bucketfuls of garden compost or well-rotted manure per square metre/yard". |
| Drainage | RHS: "Choose a sunny spot with free-draining soil". |
| Lifecycle | Hardy biennial grown as an annual: the blanched shank is harvested in the first season and stands through winter frosts. Plants flower and set seed only in a second year after cold; the crop is very frost-hardy and is not lifted for storage but left in the ground until needed. |
| Edible parts | stems (white base/shank), flower buds (scapes) |
| Documented problems | 4 diseases, 3 pests |
At a Glance
Diseases
Pests
Soil & Growing Conditions
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Sowing & Germination | 0 | Leeks are grown from seed. SOWING DEPTH: sow seed 1.5cm (about half to three-quarter inch) deep - indoors in modules or trays in late winter (keep above 10°C/50°F), or outdoors from March to April in a shallow drill, watering the base first and sowing thinly, with rows about 30cm (12in) apart. Later sowings in May-June give leeks for winter and spring. Grow the seedlings on until they are about 20cm (8in) tall and pencil-thick, ready to transplant (roughly eight weeks from an indoor sowing). |
| Transplanting & Establishment | 3 | This is the step that gives leeks their long white shank. When seedlings are pencil-thick, lift them and trim the roots to about 2.5cm (1in). PLANTING DEPTH & SPACING: with a dibber, make holes about 15cm (6in) deep and 5cm (2in) across, spacing them 15-20cm (6-8in) apart in rows 30cm (12in) apart. Drop one leek into each hole and "puddle in" by filling the hole with water - do NOT backfill with soil; the loose hole blanches the lower stem white as it grows. Water the young plants until they are established, then keep the bed weed-free so the shallow-rooted leeks are not crowded. |
| Shank Development & Blanching | 7 | Over the following months the shank thickens and lengthens. To lengthen the white (blanched) portion, draw dry soil up around the stems several times through the season (earthing up), taking care not to let soil fall into the centre of the plant. Water only during prolonged dry spells once established - leeks are shallow-rooted and drought reduces yield - and keep weeding. Watch for orange leek rust on the leaves and cover with insect-proof mesh where allium leaf miner or leek moth are a problem. |
| Harvest | 8 | Leeks can be harvested at any size: pull baby leeks from late summer, or leave plants to reach full size. They do not need lifting for storage - being very frost-hardy, they stand in the ground and are lifted fresh as needed, with hardy late cultivars cropping right through winter and into spring. Gently lift each plant with a fork rather than pulling, to avoid snapping the shank. Days from sowing to first harvest range from about 60 (baby leeks) to 180 or more for full-sized winter leeks. |
Harvest & Storage
Companion Planting
Leeks, Seed to Harvest
Plan your Leeks planting
Timing for Leeks follows soil temperature and frost, not the calendar date. The Global vegetable planting calendar explains the method. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.
Growing Leek in another region
Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.
Sources
These 2 sources are specific to this region. The full list of 14 sources behind this guide (FAO EcoCrop, Global Biodiversity Information Facility (GBIF), NC State Extension Gardener Plant Toolbox and others) is in the references of our UK guide to leeks; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
What soil pH do leeks need?
A pH of about 6–6.5. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.
What problems affect leeks?
Our data links 4 diseases and 3 pests to this crop. See the sections above for each one and how to manage it.
Plan next season before the problems start
This page gives you the thresholds; the planner turns them into your own calendar. It works from what you can observe and measure in your garden rather than from dates written for somebody else’s latitude.
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How this guide is put together
The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against international horticultural research and extension sources. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.
Last verified 2026-08-06
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Keep going
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.