How to Grow Leeks USA
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In the US, leeks aren't waiting on your last frost date — they can take cold that would kill a tomato — so what actually governs planting is your season length: start transplants indoors 6–8 weeks before setting out, then move them to the garden as soon as the ground can be worked, rather than waiting for frost to pass. Expect to harvest anywhere from about 60 days (baby leeks) to 100–120 days (full-sized) after seeding.
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 | 50°F (10°C) |
| Optimal growing temp | 64-75°F (18-24°C) |
| Minimum survivable temp | 23°F (-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
When to plant in the USA
United States. Leek is a hardy cool-season biennial, so unlike most transplanted crops it is not waiting on your frost date — it will take cold that would end a tomato. What governs it is length of season: 100-120 days to mature, though stems are usable from about 60 days after seeding. Raise transplants for 6-8 weeks before setting out, sow 1/4-1/2 in deep and thin to 4-6 in apart in rows 8-16 in apart, and hill soil up the stems as they grow to blanch a longer white shank. Harvest once stalks reach about 1 in across. Where the season is short, start indoors and plant out as early as the ground can be worked rather than waiting for the frost date to pass.
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
When to sow and plant Leeks depends on your own frost dates. Check the USA vegetable planting calendar, or the month-by-month guides that cover Leeks: January, February, March, November, December. 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
-
US extension source: leek is a hardy cool-season biennial; transplants need 6-8 weeks of growth before planting out; sow 1/4-1/2 in deep and thin to 4-6 in apart in rows 8-16 in apart; harvestable as early as 60 days after seeding but generally 100-120 days to mature; hilling blanches a longer edible stem; water to 18 in depth every 7 days; side dress 1/4 lb 21-0-0 per 100 sq ft in mid-May and again late June; harvest at 1 in stalk diameter; store at 32-40°F in humid conditions such as wet sand.
These 5 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
Almost everything on this page resolves to your own frost dates rather than the calendar — the last spring frost moves by roughly two months between zone 3 and zone 10. The USA Garden Planner works from your zone so the timing is already decided before the season starts.
Get the USA Garden Planner →Instant PDF download · Written for US growing conditions
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 USDA hardiness-zone and frost-date data, with Cooperative Extension sources cited directly where one exists for a crop. 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.
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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.