VegetablealliumStraightforward

Leek

Allium ampeloprasum

The most useful winter vegetable there is, standing in the ground from autumn until spring and needing almost nothing once planted. It is also the only common crop planted by dropping a seedling into a deep dibbed hole and watering it in rather than backfilling — the hole is what produces the long white shank.

Position: Full sun or Partial shade
Water: moderate demand
Drainage: Moisture-retentive
Grows to: 45–60 cm × 15 cm
Hardiness: H6
Harvest: October to March
Difficulty: Straightforward

Described view

A leek seedling dropped into a deep dibbed hole with the hole being filled with water rather than backfilled with soil

August

Nothing to do

No sowing, planting, harvesting or pruning window falls in August.

Leek’s year

Resolved for United Kingdom (general). Every window is stored against a climate event rather than a date, so a late frost pocket runs later than the band shows. What else August calls for.

Activity	J	F	M	A	J	J	O	N	D
Sow under cover		February.	March.
Sow outdoors			March.	April.
Pot on					June.	July.
Harvest	January.	February.	March.				October.	November.	December.

Timing that travels

The band above resolves this plant's windows into months for one region. These are the windows themselves, stored against a climate event rather than a date — which is the form that survives being carried to a colder garden, a frost pocket, or next year.

Conditions it needs

Light: Full sun, Partial shade
Frost: Very hardy
Hardiness rating: H6 (RHS)
Grows best at: 13–24 °C
Germinates at: 10–25 °C
Soil: Loam, Clay, Sandy
Soil pH: 6–7.5
Drainage: Moisture-retentive
Water needs: moderate
Drought: moderate tolerance
Waterlogging: moderate tolerance
Heat: moderate tolerance
Wind and exposure: good tolerance

Where these figures come from

LightSourced guidancemoderate confidence: Royal Horticultural Society: Leek — position
Checked 2026-08-13
FrostSourced guidancehigh confidence: Royal Horticultural Society: Leek — hardiness
Checked 2026-08-13
Hardiness ratingSourced guidancemoderate confidence: Royal Horticultural Society: RHS hardiness ratings
Checked 2026-08-13
Grows best atSourced guidancemoderate confidence: Royal Horticultural Society: Leek — temperature
Checked 2026-08-13
Germinates atSourced guidancemoderate confidence: Royal Horticultural Society: Seed germination temperatures
Checked 2026-08-13
SoilSourced guidancemoderate confidence: Royal Horticultural Society: Leek — soil
Checked 2026-08-13
Soil pHSourced guidancemoderate confidence: Plant Finder — Missouri Botanical Garden: Allium ampeloprasum — culture
Checked 2026-08-13
DrainageSourced guidancemoderate confidence: Royal Horticultural Society: Leek — soil
Checked 2026-08-13
Water needsHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
DroughtHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
WaterloggingHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
HeatHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Wind and exposureHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

On your soil

Computed by comparing this plant's recorded requirements against each soil's recorded characteristics. A recorded horticultural fact overrides the comparison where GrowingHQ holds one.

Soil	Verdict	Why
Heavy clay	Prefers this soil	Heavy clay suits Leek as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. Clay is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Sandy	Grows well here	Leek grows perfectly well on sandy without special measures, though it is not the soil it would choose.
Chalky and alkaline	Grows well here	Leek grows perfectly well on chalky and alkaline without special measures, though it is not the soil it would choose.
Loam	Prefers this soil	Loam suits Leek as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Grows well here	Leek grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acid	Grows well here	Leek grows perfectly well on peaty and acid without special measures, though it is not the soil it would choose.
Shallow over rock	Grows well here	Leek grows perfectly well on shallow over rock without special measures, though it is not the soil it would choose.
Made ground and urban soil	Grows well here	Leek grows perfectly well on made ground and urban soil without special measures, though it is not the soil it would choose.

Not sure which you have? Four hand tests will settle it.

Space and spacing

Mature height: 45–60 cm
Mature spread: 15 cm
Rooting depth: 30 cm
Spacing: 15–23 cm apart

Where these figures come from

Mature heightHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Mature spreadHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Rooting depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
SpacingSourced guidancemoderate confidence: Royal Horticultural Society: Leek — spacing
Checked 2026-08-13

Measured centre to centre. Plants set closer than this compete for light and water long before they look crowded, and the crowding cannot be undone once they are in.

In a container

Minimum volume: 10 litres or more
Minimum depth: 30 cm

Where the container figures come from

Minimum volumeHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

Where and how you can grow it

Each way of growing is assessed separately, and “not assessed” is a real answer rather than a gap we have filled in with a guess.

Method	Suitability	What it needs
Open ground	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Traditional dug bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Raised bed	Well suited source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13
Container	Workable source Sourced guidancemoderate confidence Royal Horticultural Society: Growing method suitability Checked 2026-08-13	30 cm deep so there is room to blanch the shank
Hydroponics	Marginal source GrowingHQ editorial positionmoderate confidence A long season and a crop whose whole value is a blanched white shaft, which is produced by earthing up — an operation with no soilless equivalent. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13
Greenhouse	Marginal source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Alliums under protection Checked 2026-08-13
Polytunnel	Marginal source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Alliums under protection Checked 2026-08-13
Windowsill	Marginal source Horticultural consensusmoderate confidence Royal Horticultural Society: Growing herbs and salads indoors Checked 2026-08-13

Growing it

TransplantingTrim the roots and leaf tips by about a third, dib a hole 15 cm deep, drop the seedling in and water it in. Do not backfill — soil falls in gradually as the plant grows, and the depth is what blanches the stem.
Earthing upDraw soil up around the stems as they grow, or slide a cardboard collar over them. Every centimetre covered is another centimetre of white shank, which is the part worth eating.

Where this guidance comes from

TransplantingSourced guidancehigh confidence: Royal Horticultural Society: Leek — planting
Checked 2026-08-13
Earthing upSourced guidancehigh confidence: Royal Horticultural Society: Leek — care
Checked 2026-08-13

Is it worth putting under cover?

Whether it will grow there is on the methods table above. This is whether the space is well spent, which is a different question and usually the one being asked.

Structure	What protection is worth	What decides it
Greenhouse	No real benefit source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Occupies protected ground for months to produce something that grows perfectly well outdoors. The cost is not the crop, it is everything that could have been there instead. A leek occupies ground for the best part of a year and is completely hardy.
Polytunnel	No real benefit source GrowingHQ editorial positionmoderate confidence What protection is worth for this crop, judged against the same standard as every other record in this file. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13	Occupies protected ground for months to produce something that grows perfectly well outdoors. The cost is not the crop, it is everything that could have been there instead.

On a windowsill

Does not work indoors

source

GrowingHQ editorial positionmoderate confidence

How long the crop is actually productive on an ordinary British windowsill without added light.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Not a windowsill crop. The reason is given — usually light, root volume or sheer size. Depth and season length. A leek wants deep ground for the better part of a year, and there is no small version of it.

Growing it without soil

Nearly anything can be grown in a soilless system by somebody with enough equipment. The useful question is whether it is worth it, in which technique, and what goes wrong.

Not worth it

It can be made to grow, but a soilless system is the wrong tool — usually because of rooting volume, running cost, or a result no better than a pot of compost.

source

GrowingHQ editorial positionmoderate confidence

A long season and a crop whose whole value is a blanched white shaft, which is produced by earthing up — an operation with no soilless equivalent.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Blanching by earthing up has no soilless equivalent, and a green leek is a different vegetable.

Techniques that suit it

Drip-fed mediumSolution is dripped into an inert medium around each plant. The most forgiving technique and the one that suits large, long-season, heavy crops.

Horticultural consensusDepends on conditionsmoderate confidence

Applies when: Possible, and the result is a green leek.

No external citation — see the evidence type above.

Checked 2026-08-13

Root space: Deep, for the blanched length rather than for the roots.
pH band: 5.5–6.5

Where these figures come from

Root spaceHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

pH bandSourced guidancehigh confidence

Outside roughly this band, individual nutrients become unavailable even when they are present in the solution — which is why a crop can starve in a full reservoir.

Purdue Extension — Purdue University: Hydroponic solution management — pH

Checked 2026-08-13

No nutrient recipes here

GrowingHQ records pH bands, which are measurable properties of nutrient availability, and deliberately records no EC or PPM targets and no mixing instructions. Published targets vary by cultivar, growth stage, water source and technique, and the figures that apply to your system are on the product you bought.

Harvesting

When it is readyLift from autumn onwards at whatever size is wanted. There is no need to harvest the row at once — leeks hold in the ground for months.
How to pick itLift with a fork rather than pulling — a leek pulled from firm ground usually parts company with its roots and comes up as a handful of leaves. Loosen alongside the row and lever the plant up whole. Leeks stand in the ground through the winter in good condition, so lift them as they are wanted rather than all at once.

Where the harvest guidance comes from

When it is readySourced guidancehigh confidence: Royal Horticultural Society: Leek — harvesting
Checked 2026-08-13
How to pick itSourced guidancehigh confidence: Royal Horticultural Society: Leek — harvesting
Checked 2026-08-13

What goes wrong

Problem	How often	Notes
Allium white rot	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	The same soil-borne fungus that affects onions, and it persists in the soil for many years.
Slugs and snails	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13

Sources for this page

Agriculture and Horticulture Development Board · GrowingHQ editorial synthesis · Plant Finder · Royal Horticultural Society

Each figure on this page carries its own citation, under the “where these figures come from” note in its section. Record last reviewed 2026-08-14.