VegetablealliumStraightforward

Garlic

Allium sativum

The crop that most rewards planting at the right time of year and punishes getting it wrong in a way nothing else does. Garlic needs a period of cold to split into cloves, so it is planted in autumn and lifted the following summer. Planted in spring it grows perfectly well and produces a single undivided round instead of a head — not a failure of care, but a failure of timing.

Position: Full sun
Water: low demand
Drainage: Free-draining
Grows to: 45–60 cm × 15 cm
Hardiness: H6
Harvest: June and July
Difficulty: Straightforward

Described view

Curling flower stems rising from a row of hardneck garlic plants, one being cut at the base

August

Nothing to do

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

Coming next month: plant.

Garlic’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	J	J	S	O	N	D
Plant				September.	October.	November.
Harvest		June.	July.
Dormant	January.						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.

Plant
from 6 weeks before to 4 weeks after your first autumn frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Garlic — when to plant
Checked 2026-08-13
Autumn planting. The cold period through winter is what makes the clove divide into a head.

Conditions it needs

Light: Full sun
Direct sun: 6 hours a day or more
Frost: Very hardy
Hardiness rating: H6 (RHS)
Survives down to: -10–0 °CSourced guidanceDepends on conditions
Germinates at: 0–10 °C
Soil: Loam, Sandy
Soil pH: 6–7.5
Drainage: Free-draining
Water needs: low
Drought: moderate tolerance
Waterlogging: poor tolerance
Heat: moderate tolerance
Wind and exposure: good tolerance

Where these figures come from

LightSourced guidancehigh confidence

Royal Horticultural Society: Garlic — position

Checked 2026-08-13

Direct sunHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

FrostSourced guidancehigh confidence

Cold is a requirement rather than a threat: garlic needs it to form cloves.

Royal Horticultural Society: Garlic — hardiness

Checked 2026-08-13

Hardiness ratingSourced guidancehigh confidence

Royal Horticultural Society: RHS hardiness ratings

Checked 2026-08-13

Survives down toSourced guidanceDepends on conditionshigh confidence

Applies when: Survives well below freezing in the ground; the risk in a British winter is waterlogging, not cold.

Royal Horticultural Society: Garlic — hardiness

Checked 2026-08-13

Germinates atHorticultural consensusmoderate confidence

Not germination in the usual sense — garlic is grown from cloves, and the cold period below about 10 °C is what triggers bulb formation.

No external citation — see the evidence type above.

Checked 2026-08-13

SoilSourced guidancehigh confidence

Royal Horticultural Society: Garlic — soil

Checked 2026-08-13

Soil pHSourced guidancehigh confidence

Home and Garden Information Center — Clemson Cooperative Extension: Garlic — culture

Checked 2026-08-13

DrainageSourced guidancehigh confidence

Royal Horticultural Society: Garlic — 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 consensushigh confidence

Sitting in wet ground over winter is the commonest cause of failure in Britain.

Royal Horticultural Society: Garlic — soil

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	Works, with one condition	Garlic will crop on heavy clay, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Sandy	Prefers this soil	Sandy suits Garlic as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. Sandy soil is among the soils it is recorded as suiting.
Chalky and alkaline	Grows well here	Garlic 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 Garlic as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Silty	Prefers this soil	Silty suits Garlic as it stands: The pH suits it: it wants 6 to 7.5, and this soil is in that range. The free drainage is exactly what it wants. The soil holds moisture, which saves a great deal of watering.
Peaty and acid	Works, with one condition	Garlic will crop on peaty and acid, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.
Shallow over rock	Prefers this soil	Shallow over rock suits Garlic as it stands: The free drainage is exactly what it wants. Loam is among the soils it is recorded as suiting.
Made ground and urban soil	Works, with one condition	Garlic will crop on made ground and urban soil, but one thing has to be dealt with first. It needs ground that drains, and this soil holds water. A plant that stays in the ground through winter with its roots in cold, saturated soil rots — which is what kills most of what fails on heavy ground, rather than the cold.Improve the drainage before planting — a raised bed, or bulky organic matter worked in over several seasons. Do not add sand to clay in small quantities; it makes the problem worse.

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 cm apart
Row spacing: 30 cm

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 guidancehigh confidence: Royal Horticultural Society: Garlic — spacing
Checked 2026-08-13
Row spacingSourced guidancehigh confidence: Royal Horticultural Society: Garlic — 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: 20 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

Works better in containers than onions do, because the crop is worth more per plant and a raised container solves the winter drainage problem.

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 guidancehigh confidence Royal Horticultural Society: Garlic Checked 2026-08-13	Free-draining ground over winter
Raised bed	Well suited source Sourced guidancehigh confidence Royal Horticultural Society: Garlic — soil Checked 2026-08-13	The best option on heavy ground, because winter drainage is the whole problem.
Traditional dug bed	Well suited source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Container	Workable source Horticultural consensusmoderate confidence Royal Horticultural Society: Garlic in containers Checked 2026-08-13	A pot left outdoors through winter so the cold requirement is met
Polytunnel	Marginal source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Garlic — vernalisation Checked 2026-08-13
Hydroponics	Marginal source GrowingHQ editorial positionmoderate confidence Garlic needs a sustained cold period to split into cloves. An indoor system held at a comfortable growing temperature produces a single undivided round — not a failure of technique but of the plant's requirements being incompatible with the environment. GrowingHQ editorial synthesis — GrowingHQ Checked 2026-08-13
Greenhouse	Marginal source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Garlic — vernalisation Checked 2026-08-13
Windowsill	Not suitable source Horticultural consensusmoderate confidence No cold period, so no bulb. No external citation — see the evidence type above. Checked 2026-08-13

Growing it

PlantingSplit a bulb into cloves at planting time, not before, and push each one in point upwards with the tip about 2 cm below the surface. Plant certified seed garlic rather than a supermarket bulb, which may carry virus and is often a cultivar suited to a warmer climate.2–5 cm
WateringRarely needs watering in a British winter and spring. Stop watering entirely once the leaves begin to yellow.
HarvestingOn hardneck cultivars, cut off the flower stem — the scape — when it curls. It is edible and worth eating, and removing it sends the plant's resources into the bulb.
FeedingGarlic wants a firm, well-drained bed with compost worked in the autumn before planting rather than fresh manure, which encourages rot. A nitrogen feed in early spring as growth resumes helps bulb size; stop feeding once the bulbs begin to swell or they store badly.

Where this guidance comes from

PlantingSourced guidancehigh confidence: Royal Horticultural Society: Garlic — planting
Checked 2026-08-13
WateringHorticultural consensusmoderate confidence: Royal Horticultural Society: Garlic — watering
Checked 2026-08-13
HarvestingSourced guidancehigh confidence: Royal Horticultural Society: Garlic — scapes
Checked 2026-08-13
FeedingSourced guidancemoderate confidence: Royal Horticultural Society: Garlic — cultivation
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	Worse under cover 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	A genuine cold requirement. Garlic needs several weeks below about 10 °C to divide into cloves, and a bulb grown warm produces a single undivided round.This is the clearest counterproductive case in the file, because it is a mechanism rather than a matter of degree. The protection does not merely waste space; it prevents the crop.
Polytunnel	Worse under cover 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	The same cold requirement, slightly less badly denied because a tunnel runs colder overnight.

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

Garlic needs a sustained cold period to split into cloves. An indoor system held at a comfortable growing temperature produces a single undivided round — not a failure of technique but of the plant's requirements being incompatible with the environment.

GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

The clearest case in this file of a crop that is defeated by what a controlled environment is FOR — the absence of winter.

Techniques that suit it

Ebb and flowA bed of inert medium floods and drains on a timer. The medium holds moisture between floods, which makes it far more tolerant of interruption than NFT.

source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Root space: Modest, but irrelevant given the cold requirement.
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

Time from sowing or planting: 32–40 weeks

source

Sourced guidancehigh confidence

From autumn planting to midsummer lifting — one of the longest occupations of ground in the vegetable garden.

Royal Horticultural Society: Garlic — timing

Checked 2026-08-13

When it is readyLift when about half the leaves have yellowed, usually midsummer. Left too long the bulb splits its wrapper and will not store; lifted too early it has not filled.
How to pick itLoosen with a fork and lift; never pull by the stem.
Keeping itDry for two to three weeks in an airy place out of direct sun, then store cool and dry. Softneck cultivars keep considerably longer than hardnecks and are the ones traditionally plaited.

Where the harvest guidance comes from

When it is readySourced guidancehigh confidence: Royal Horticultural Society: Garlic — harvesting
Checked 2026-08-13
How to pick itHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13
Keeping itSourced guidancehigh confidence: Royal Horticultural Society: Storing garlic
Checked 2026-08-13

What goes wrong

Problem	How often	Notes
Scape formation in hardneck garlic	common source Sourced guidancehigh confidence Royal Horticultural Society: Garlic — cultivation Checked 2026-08-13	On hardneck cultivars, every year. Snap it off and cook it — the bulb fills better without it.
Bulb ripening	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	Ripening rather than a fault. The yellowing tops are the signal to stop watering and lift.
Allium white rot	occasional source Sourced guidancehigh confidence Royal Horticultural Society: Onion white rot Checked 2026-08-13	The reason not to plant supermarket garlic or accept cloves from an unknown plot.
Aphids	uncommon source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13

Grown with, grown after, grown instead

Every relationship states its mechanism. A pairing nobody can explain is a pairing nobody has checked, and it does not go in.

Same rotation groupOnion
Both Allium species sharing white rot and other soil-borne allium problems, so they occupy one rotation group and must not follow each other.
source
Sourced guidancehigh confidence
Royal Horticultural Society: Crop rotation
Checked 2026-08-13
Closely relatedChives
Both Allium species with the same soil-borne disease risks, so a permanent chive clump on ground intended for garlic rotation is worth reconsidering.
source
Horticultural consensusmoderate confidence
Royal Horticultural Society: Alliums
Checked 2026-08-13

Safety and edibility

Cats and dogsCan be dangerous — treat as urgent

Listed as harmful to cats or dogs

Garlic is listed as harmful if eaten. The same organosulfur chemistry as onion and more concentrated by weight, so a smaller quantity does the same damage to red blood cells. The delay between eating it and the anaemia appearing is what makes it dangerous: an animal seems fine for a day or two.

source

Sourced guidancehigh confidence

ASPCA Animal Poison Control Center — toxic and non-toxic plant list — American Society for the Prevention of Cruelty to Animals: Allium sativum — toxic plants list
Veterinary Poisons Information Service — VPIS, London: Allium sativum — clinical effects

Checked 2026-08-13

Affected parts: bulb, leaf.

Pets and livestockpets
Garlic, like other alliums, damages red blood cells in dogs and cats, with cats more sensitive again. Drying bulbs left within reach are a realistic exposure route.
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Plants harmful to pets
Checked 2026-08-13
Dry and store the crop where pets cannot reach it.

Sources for this page

Agriculture and Horticulture Development Board · GrowingHQ editorial synthesis · Home and Garden Information Center · 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 2026-08-13.

If something is wrong with it

Plant running up to flower before it is ready to eat — 2 causes GrowingHQ holds for garlic
Lower leaves turning yellow — 2 causes GrowingHQ holds for garlic

Something else? Work through it with the diagnostic tool.