GrowingHQ
VegetablebrassicaDemanding

Cauliflower

Brassica oleracea

The least forgiving brassica, and the one most likely to produce a head the size of a golf ball. Cauliflower wants rich firm ground, steady moisture and no check at any point — a dry fortnight in midsummer produces a curd that opens and is effectively over. It is worth growing well and not worth growing casually.

Position
Full sun or Partial shade
Water
high demand
Drainage
Moisture-retentive
Grows to
45–60 cm × 50–60 cm
Hardiness
H4
Harvest
July to October
Difficulty
Demanding

Described view

A cauliflower head at the correct stage for cutting, with the curd tight and the segments not yet separating, beside one that has begun to open

August

Harvest

Cauliflower’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.

ActivityJFMAMJJASOND
Sow under coverMarch. April.
Sow outdoorsApril. May.
Plant outMay. June.
HarvestJuly. August. September. October.

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 out4–8 weeks after your last spring frost
    source

    Sourced guidancehigh confidence

    • Royal Horticultural Society: Cauliflower — plant out

    Checked 2026-08-13

    Firm the soil hard around the plant. A brassica in loose ground rocks in the wind and never bulks up.

Conditions it needs

Light
Full sun, Partial shade
Frost
Hardy
Hardiness rating
H4 (RHS)
Grows best at
15–20 °C
Germinates at
10–25 °C
Soil
Loam, Clay
Soil pH
6.5–7.5
Drainage
Moisture-retentive
Water needs
high
Drought
poor tolerance
Waterlogging
moderate tolerance
Heat
poor tolerance
Wind and exposure
moderate tolerance
Where these figures come from
LightSourced guidancemoderate confidence
  • Royal Horticultural Society: Cauliflower — position

Checked 2026-08-13

FrostSourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — 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: Cauliflower — 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: Cauliflower — soil

Checked 2026-08-13

Soil pHSourced guidancemoderate confidence
  • Plant Finder — Missouri Botanical Garden: Brassica oleracea — culture

Checked 2026-08-13

DrainageSourced guidancemoderate confidence
  • Royal Horticultural Society: Cauliflower — soil

Checked 2026-08-13

Water needsHorticultural consensusmoderate confidence

Consistency matters more than quantity. A dry spell followed by heavy watering is worse than steady moderate watering.

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

Heat during curd formation causes the head to open.

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.

SoilVerdictWhy
Heavy clayPrefers this soilHeavy clay suits Cauliflower as it stands: The pH suits it: it wants 6.5 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.
SandyWorks, with one conditionCauliflower will crop on sandy, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Chalky and alkalineWorks, with one conditionCauliflower will crop on chalky and alkaline, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
LoamPrefers this soilLoam suits Cauliflower as it stands: The pH suits it: it wants 6.5 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.
SiltyGrows well hereCauliflower grows perfectly well on silty without special measures, though it is not the soil it would choose.
Peaty and acidGrows well hereCauliflower grows perfectly well on peaty and acid without special measures, though it is not the soil it would choose.
Shallow over rockWorks, with one conditionCauliflower will crop on shallow over rock, but one thing has to be dealt with first. It has little drought tolerance and this soil dries out fast — it will check and bolt in the first dry spell without watering.Water and mulch will carry it through. On this soil the watering is not optional in a dry spell, which is the difference between a crop and a failure.
Made ground and urban soilGrows well hereCauliflower 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
50–60 cm
Rooting depth
45 cm
Spacing
60–75 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: Cauliflower — spacing

Checked 2026-08-13

How far apart to plant cauliflowerThree cauliflower plants drawn in a row at their recorded spacing of 60–75 cm between plants. The spacing is drawn to scale against a one metre rule; the plants themselves are symbols rather than scale drawings, so the distance between them is the part to read.60–75 cmone metre
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
20 litres or more
Minimum depth
40 cm
Where the container figures come from
Minimum volumeSourced guidancehigh confidence

Possible and rarely satisfying: the plant is large, hungry and needs firm ground, none of which a container does well.

  • Royal Horticultural Society: Brassicas in containers

Checked 2026-08-13

Minimum depthHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Possible but rarely worth it: cauliflowers need constant moisture and steady feeding to make a head, and a container makes both harder. Grow a summer variety and expect a smaller curd.

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.

MethodSuitabilityWhat it needs
Open groundWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Traditional dug bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

Raised bedWell suited
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

GreenhouseWorkable
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

PolytunnelWorkable
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

ContainerMarginal
source

Sourced guidancemoderate confidence

  • Royal Horticultural Society: Growing method suitability

Checked 2026-08-13

20 litres and firm compost; Reliable watering
HydroponicsMarginal
source

GrowingHQ editorial positionmoderate confidence

The same occupancy argument as cabbage with less tolerance: a cauliflower checked at any point in its long season makes a button curd instead of a head, and a soilless system offers more ways to check it than soil does.

  • GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

Growing it

  • WateringWater deeply and regularly from transplanting to harvest. The curd forms in a short window and a check during it cannot be recovered from — this is the whole of cauliflower growing.
  • ProtectionSnap a couple of the plant's own outer leaves over the developing curd on a summer cauliflower. It keeps the head white; sun turns it yellow and makes it look worse than it tastes.
  • FeedingFeed generously before planting and again in midsummer. Cauliflower is the hungriest brassica and a small head is more often underfeeding than underwatering.
  • HarvestingCut the whole head with a few leaves left around it to protect the curd. Cauliflowers do not wait: a head that is not cut within a few days of reaching size begins to open into separate florets and is past its best, so check the bed every two or three days once the curds are visible.
Where this guidance comes from
WateringSourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — care

Checked 2026-08-13

ProtectionSourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — blanching

Checked 2026-08-13

FeedingSourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — care

Checked 2026-08-13

HarvestingSourced guidancemoderate confidence
  • Royal Horticultural Society: Cauliflowers — harvesting

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.

StructureWhat protection is worthWhat decides it
GreenhouseNo 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.
PolytunnelNo 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.

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

The same occupancy argument as cabbage with less tolerance: a cauliflower checked at any point in its long season makes a button curd instead of a head, and a soilless system offers more ways to check it than soil does.

  • GrowingHQ editorial synthesis — GrowingHQ

Checked 2026-08-13

The curd is a stalled flower head, which is why anything that checks the plant shows up in the part you eat.

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: Only the most forgiving technique, and still not worth the months.

No external citation — see the evidence type above.

Checked 2026-08-13

Root space
Substantial, and held for the whole season.
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

What actually goes wrong

  • Pump or power failure. In nutrient film and aeroponics there is no reserve at the roots, so a crop can be lost within hours; medium-based systems hold moisture and are far more forgiving.
    source

    Sourced guidancehigh confidence

    • Purdue Extension — Purdue University: Hydroponic system design — failure modes

    Checked 2026-08-13

  • pH drift. The solution moves as the plants take nutrients up, and by the time deficiency symptoms appear on the leaves the cause is several weeks old.
    source

    Sourced guidancehigh confidence

    • 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 readyCut while the curd is still tight and the segments have not begun to separate. Once it starts to open it deteriorates within a day or two.
  • How to pick itCut the whole stem through with a sharp knife well below the curd, taking a collar of the surrounding leaves with it — they protect the curd on the way to the kitchen and keep it white. Cut in the morning while the head is cool and firm. The plant will not produce a second head, so the stump can come out at the same time.
  • Keeping itA fortnight in a fridge. Cauliflower freezes well after blanching, which is what to do with a glut arriving all at once.
Where the harvest guidance comes from
When it is readySourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — harvesting

Checked 2026-08-13

How to pick itSourced guidancehigh confidence
  • Royal Horticultural Society: Cauliflower — harvesting

Checked 2026-08-13

Keeping itHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

What goes wrong

ProblemHow oftenNotes
Flea beetlecommon
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Cabbage root flycommon
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Transplants are the vulnerable stage; a collar or mesh at planting is the control.
Clubrootcommon
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Cabbage white caterpillarscommon
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Slugs and snailscommon
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Aphidsoccasional
source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Sources for this page

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.