VegetablebrassicaStraightforward

Kale

Brassica oleracea

The most useful winter vegetable a small garden can grow. Kale is the hardiest of the common brassicas, stands through frost and snow, and is picked leaf by leaf over months rather than cut all at once — so one plant feeds a household repeatedly. It is also the easiest brassica: it makes no head, so there is nothing to fail to heart.

Position: Full sun or Partial shade
Water: moderate demand
Drainage: Moisture-retentive
Grows to: 45–90 cm × 45–60 cm
Hardiness: H6
Harvest: October to April
Difficulty: Straightforward

Described view

A curly kale plant in winter with frost on its deeply crinkled blue-green leaves, lower leaves already picked

August

Plant out

Kale’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	M	J	J	A	O	N	D
Sow outdoors				April.	May.	June.	July.
Plant out						June.	July.	August.
Harvest	January.	February.	March.	April.					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.

Sow outdoors
0–10 weeks after your last spring frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Kale — sowing
Checked 2026-08-13
Sown in late spring for a crop that stands through the following winter.
Plant out
6–14 weeks after your last spring frost
source
Sourced guidancehigh confidence
- Royal Horticultural Society: Kale — planting out
Checked 2026-08-13

Conditions it needs

Light: Full sun, Partial shade
Direct sun: 4 hours a day or more
Frost: Very hardy
Hardiness rating: H6 (RHS)
Survives down to: -15–-10 °CSourced guidanceDepends on conditions
Grows best at: 10–22 °C
Germinates at: 7–30 °C
Soil: Loam, Clay, Silt
Soil pH: 6.5–7.5
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 guidancehigh confidence

One of the more shade-tolerant productive vegetables, which matters for a small or overlooked garden.

Royal Horticultural Society: Kale — position

Checked 2026-08-13

Direct sunHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

FrostSourced guidancehigh confidence

Royal Horticultural Society: Kale — 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: Cultivar-dependent; curly kales are generally the toughest.

Royal Horticultural Society: Kale — hardiness

Checked 2026-08-13

Grows best atHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Germinates atSourced guidancehigh confidence

OSU Extension Service — Oregon State University: Vegetable seed germination temperatures

Checked 2026-08-13

SoilHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Soil pHSourced guidancehigh confidence

Royal Horticultural Society: Brassicas — soil pH

Checked 2026-08-13

DrainageHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

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 exposureSourced guidancehigh confidence

Tall cultivars still benefit from firming or staking on windy sites.

Royal Horticultural Society: Kale — exposed sites

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 Kale 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.
Sandy	Grows well here	Kale grows perfectly well on sandy without special measures, though it is not the soil it would choose.
Chalky and alkaline	Grows well here	Kale 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 Kale 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.
Silty	Prefers this soil	Silty suits Kale as it stands: The pH suits it: it wants 6.5 to 7.5, and this soil is in that range. Silt is among the soils it is recorded as suiting. The soil holds moisture, which saves a great deal of watering.
Peaty and acid	Grows well here	Kale 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	Kale 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	Kale 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: 45–90 cm
Mature spread: 45–60 cm
Rooting depth: 45 cm
Spacing: 45 cm apart
Row spacing: 45–60 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: Kale — spacing
Checked 2026-08-13
Row spacingSourced guidancehigh confidence: Royal Horticultural Society: Kale — 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: 15–20 litres
Minimum depth: 30 cm

Where the container figures come from

Minimum volumeSourced guidancehigh confidence: Royal Horticultural Society: Kale in containers
Checked 2026-08-13
Minimum depthHorticultural consensusmoderate confidence: No external citation — see the evidence type above.
Checked 2026-08-13

A genuinely good container crop: it stands all winter, looks well, and is picked a leaf at a time.

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: Kale Checked 2026-08-13	Netting against pigeons through winter
Traditional dug bed	Well suited source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Raised bed	Well suited source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Container	Well suited source Sourced guidancehigh confidence Royal Horticultural Society: Kale in containers Checked 2026-08-13	15 litres or more per plant
Polytunnel	Well suited source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Brassicas under protection Checked 2026-08-13	For tender baby leaves in winter rather than for the standing crop.
Aquaponics	Well suited source Sourced guidancemoderate confidence Purdue Extension — Purdue University: Aquaponic leafy greens Checked 2026-08-13
Greenhouse	Well suited source Sourced guidancemoderate confidence Agriculture and Horticulture Development Board — AHDB: Brassicas under protection Checked 2026-08-13
Hydroponics	Workable source Sourced guidancemoderate confidence Purdue Extension — Purdue University: Hydroponic leafy greens Checked 2026-08-13
Windowsill	Marginal source Horticultural consensusmoderate confidence Only as baby leaves cut young; a mature kale plant is far too large. No external citation — see the evidence type above. Checked 2026-08-13

Growing it

TransplantingPlant firmly and deeply, up to the lowest leaves. Kale is top-heavy by winter and a loosely planted one rocks itself out of the ground.
ProtectionNet against pigeons, which do far more damage to kale in January than caterpillars do in July.
HarvestingPick a few of the lower leaves from each plant, leaving the growing point intact. Handled this way a kale plant crops from autumn until it runs to flower in spring.
WateringWater well when transplanting and in dry spells until the plants are established; after that kale is among the most drought-tolerant brassicas and needs little. Plants that check from dryness while young stay small all season rather than catching up.
FeedingBrassicas want nitrogen and firm ground. Work in compost before planting and give a nitrogen-rich top dressing in late summer for plants that will stand through the winter, which is when they are picked hardest and have least growing weather to recover in.

Where this guidance comes from

TransplantingSourced guidancehigh confidence: Royal Horticultural Society: Brassicas — planting
Checked 2026-08-13
ProtectionSourced guidancehigh confidence: Royal Horticultural Society: Brassicas — protection
Checked 2026-08-13
HarvestingSourced guidancehigh confidence: Royal Horticultural Society: Kale — harvesting
Checked 2026-08-13
WateringSourced guidancemoderate confidence: Royal Horticultural Society: Kale — cultivation
Checked 2026-08-13
FeedingSourced guidancemoderate confidence: Royal Horticultural Society: Kale — feeding
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. Kale is among the hardiest things in the catalogue and stands a British winter without help.
Polytunnel	Extends the season 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	Leaf quality rather than survival. The plant is fine outside; a tunnel keeps the leaves clean and pickable in February mud.

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.

Works with conditions

Succeeds when the conditions listed here are met and fails when they are not. The conditions are the answer, not a caveat.

source

Sourced guidancemoderate confidence

Purdue Extension — Purdue University: Hydroponic leafy greens

Checked 2026-08-13

Works as a baby-leaf crop. Growing a full-sized plant under lights spends a great deal on something that is hardy to −10 °C outside.

Techniques that suit it

Deep water cultureRoots hang in aerated solution. Very productive and very unforgiving of solution temperature — warm solution holds less oxygen and root disease follows.
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.
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.

source

Horticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Root space: Larger than lettuce; a mature kale plant is substantial and needs a bed rather than a channel.
Lighting: Needs supplementary light
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

LightingHorticultural 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

Occupying a lot of expensive lit space for a crop that stands outdoors through a British winter unprotected.
source
GrowingHQ editorial positionmoderate confidence
A judgement about value rather than about the plant, which grows perfectly well in solution.
- GrowingHQ editorial synthesis — GrowingHQ
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: 20–26 weeks

source

Sourced guidancehigh confidence

Royal Horticultural Society: Kale — timing

Checked 2026-08-13

When it is readyStart picking once the plant is well established and take young leaves in preference to old tough ones. Flavour is widely reported to improve after frost, as cold weather increases sugar concentration in the leaves.Sourced guidanceDepends on conditions
How to pick itSnap or cut individual leaves at the stem, working from the bottom of the plant upwards.
Keeping itA few days in a refrigerator. Better left standing in the garden and picked as needed.

Where the harvest guidance comes from

When it is readySourced guidanceDepends on conditionshigh confidence

Applies when: The sweetening effect of cold is well described for kale and other winter brassicas, but the size of it varies by cultivar and by how hard the frost was.

Royal Horticultural Society: Kale — harvesting

Checked 2026-08-13

How to pick itHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Keeping itHorticultural consensusmoderate confidence

No external citation — see the evidence type above.

Checked 2026-08-13

Keep picking

Regular picking keeps this plant producing. Fruit or leaves left to mature signal it to slow down or stop.

What goes wrong

Problem	How often	Notes
Cabbage root fly	common 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.
Flea beetle	common source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Cabbage white caterpillars	common source Sourced guidancehigh confidence Royal Horticultural Society: Cabbage caterpillars Checked 2026-08-13	Damage matters more here than on a heading cabbage, because the leaves are the crop.
Aphids	common source Sourced guidancehigh confidence Royal Horticultural Society: Mealy cabbage aphid Checked 2026-08-13	Mealy cabbage aphid colonises the growing point and is hard to wash out of curly cultivars.
Clubroot	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Slugs and snails	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13
Bolting	occasional source Horticultural consensusmoderate confidence No external citation — see the evidence type above. Checked 2026-08-13	In its second spring, which is the natural end of a biennial's life rather than a failure.

Start from what you can see

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 groupCabbage
The same species as cabbage and broccoli in a different cultivar group, sharing clubroot and every brassica pest, so all three occupy one rotation slot.
source
Sourced guidancehigh confidence
GRIN Taxonomy — United States Department of Agriculture, Agricultural Research Service: Brassica oleracea cultivar groups
Checked 2026-08-13
Alternative toSpinach
Where spinach bolts in summer and dies back in winter, kale supplies leaves through the months spinach cannot — a straightforward substitution for anyone wanting greens in January.
source
Sourced guidancehigh confidence
Royal Horticultural Society: Winter leafy vegetables
Checked 2026-08-13

Sources for this page

Agriculture and Horticulture Development Board · OSU Extension Service · Purdue Extension · 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 kale
Lower leaves turning yellow — 2 causes GrowingHQ holds for kale

Something else? Work through it with the diagnostic tool.