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How to Grow Leeks Canada | Care, Pests & Disease Control

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Leek (Allium ampeloprasum var. porrum)

A bed of leeks growing on a UK allotment with a shed behind. Photo: John C, CC BY-SA 2.0, via Wikimedia Commons.

13 sources cited · Verified

The short answer

Ready in
60–180 days
Site
6+ hours of sun, soil pH 6–6.5
Biggest risk
Allium white rot

In the UK, leeks are ready to harvest 60–180 days after planting.

Leeks (Allium ampeloprasum var. porrum) — Hardy biennial grown as an annual.

This crop carries an unusually heavy problem load: 4 diseases, 3 pests and 0 nutrient issues are documented for it, so most of the effort in growing it well goes into prevention.

Core growing advice on this page is checked against named horticultural and university-extension sources — see References.

Diseases

Allium white rot
severe

Stromatinia cepivora (syn. Sclerotium cepivorum)

RHS: "Onions, garlic, leeks and other alliums".

Leek rust
moderate_to_severe

Puccinia porri (syn. Puccinia allii)

RHS: "Leeks, garlic, onions, chives, and other Allium species".

Fusarium basal rot
high_once_symptomatic

Fusarium oxysporum f. sp. cepae (also Fusarium proliferatum)

UC IPM names leek explicitly among affected Allium crops.

Onion downy mildew
moderate_to_severe

Peronospora destructor

UC IPM names leek among the hosts: "Garlic, onion, shallot, chives, and leek". Neither RHS page listed leek, so this crop link exists only because a second country's source was consulted.

Pests

Leek moth
high

Acrolepiopsis assectella

RHS: affects "Leek, onion, shallot, garlic".

Onion fly
moderate

Delia antiqua

RHS onion fly page: affects "Onion, shallots, and leeks".

Allium leaf miner
high

Phytomyza gymnostoma

RHS: affects "Leeks, onion, chives, shallot and garlic".

Quick Facts

Factor Value
Soil pH 6 - 6.5
Sunlight 6-10 hours direct sun
Germination temp 10C
Optimal growing temp 18-24C
Minimum survivable temp -5C
Time to harvest 60-180 days
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)

At a Glance

Allium ampeloprasum var… Leek Allium white rot Leek rust Fusarium basal rot Onion downy mildew Leek moth Onion fly Allium leaf miner DISEASES PESTS

When to plant in Canada

Canada. Leek is hardy enough to ignore the frost date, so the Canadian question is arithmetic rather than protection: 100-120 days to maturity against your region's frost-free window. Against the Environment and Climate Change Canada normals that means it finishes comfortably on the Pacific coast (237 frost-free days), in the Inland Valleys and Southern Lakes (168) and in Atlantic Maritime (163); it is workable but tight on the Prairies (117), where an indoor start of 6-8 weeks is doing the real work; and it will not reliably mature outdoors in the Far North and Alpine region (81) without protection. Hill soil up the stems to blanch a longer shank, harvest at about 2.5 cm across, and store at 0-4C in damp sand.

Soil & Growing Conditions

Rows of leeks growing in a field with farm buildings behind — "Leeks growing on Homestead Farm, Holmeswood" by Mike Pennington is licensed under CC BY-SA 2.0. Source: Wikimedia Commons
“Leeks growing on Homestead Farm, Holmeswood” by Mike Pennington is licensed under CC BY-SA 2.0. Source: Wikimedia Commons.

Water: RHS: water seedlings and young plants until established, then "only during prolonged dry spells". Univ. of Maryland: "Leeks require regular watering throughout growth for best production...rooting depth in leeks is shallow. Drought stress will decrease yield".

Soil pH range

6 6.5

Span reflects genuine variation between the cited authorities, not a single agreed figure.

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 10C/50F), 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

Two bunches of harvested leeks with long white blanched shanks — "Bunches of leeks at market" by RIOS269611 is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Bunches of leeks at market” by RIOS269611 is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

When to pick: RHS: "You can harvest leeks at any size" -- baby leeks take "only a couple of months, while full-sized leeks can take six months". Univ. of Maryland: "Leeks are ready to eat when the stalks are 1 inch in diameter", harvestable "as early as 60 days after planting" but generally requiring 100-120 days to mature.

Storage

Univ. of Maryland: "Leeks can be stored for 7 to 10 days in a refrigerator", or "overwintered in the garden and dug as necessary". RHS states no storage method.

Companion Planting

avoid shared disease

Allium cepa

Both crops are documented hosts of Allium white rot. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew -- so…

avoid shared disease

Allium sativum

Both crops are documented hosts of Allium white rot. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew -- so…

avoid shared disease

Allium cepa Aggregatum Group

Both crops are documented hosts of Allium white rot. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew -- so…

References

  1. country=INTL

  2. country=International

  3. Qualitative only: southern/coastal last air frost often before end of April; further north well into May, in a few places into June. No numeric per-region frost dates published here.

  4. country=UK

  5. country=UK

  6. country=UK

  7. country=UK

  8. country=UK

  9. country=UK

  10. country=USA

  11. country=USA

  12. country=USA

  13. Tier 1. 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 32-40F in humid conditions such as wet sand.

13 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.

Frequently Asked Questions

How long do leeks take to grow?

Typically 60–180 days, depending on cultivar and growing conditions.

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

Short-season growing is arithmetic before it is technique: days to maturity against frost-free days decides what will finish at all. The Canada Garden Planner does that subtraction for your region before you sow.

Get the Canada Garden Planner →

Instant PDF download · Written for Canadian growing conditions

SoilCommander Editorial Team

Canadian vegetable growing guides · Checked against provincial agriculture & university extension guidance

Every SoilCommander guide is written and maintained by our editorial team for real Canadian growing conditions, and checked against provincial agriculture and Canadian university extension guidance, and against frost-date and growing-season data, before publication.

Vegetable Growing Guides Canada

Last verified 2026-08-06

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