Plant care
Curly Kaletemperature & humidity
Brassica oleracea var. sabellica 'Curly Kale'
More about curly kale
Ideal temperature for curly kale
Aim for 7-24°C (45-75°F) on the thermostat and you've handled the easy part. The hard part is the half-metre around the plant: window glass that drops to near-freezing on a January night, a radiator pumping out hot dry air, a draught from an opened front door. Move the plant 30 cm and you've usually fixed the problem. Below roughly 7°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Curly Kale is comparatively hardy (USDA 7-10 (overwinters); grown as an annual or biennial in zones 2-11, RHS H5). Within that range it tolerates a cold dormant spell outdoors; outside it, grow it in a container you can move under cover or overwinter in a cool but frost-free spot. Hardiness assumes an established plant in well-drained soil — a wet, cold root zone kills far more plants than cold air alone.
Humidity for curly kale
Curly Kale sits happiest at around 50-70% relative humidity. Adaptable to outdoor humidity; good airflow matters more than the level itself. Still, humid, crowded plantings encourage powdery mildew, downy mildew and aphid build-up, so space plants well. The usual low-humidity tell is crisp brown leaf tips and edges while the soil moisture is fine — a sign the air, not the watering, is the problem. If you need to raise it, the reliable methods are grouping plants together, standing the pot on a tray of damp pebbles (the pot above the waterline, never in it), or running a small humidifier in winter when indoor heating dries the air most. Misting is the least effective — it raises humidity for minutes, not hours.
Curly Kale temperature & humidity — frequently asked questions
What temperature is best for curly kale?
Curly Kale grows best between 7-24°C (45-75°F). Keep it out of cold draughts, off freezing windowsills in winter, and away from the hot dry air directly above radiators — the extremes matter far more than the average room temperature.
How cold can curly kale tolerate?
Curly Kale starts to suffer below roughly 7°C. It tolerates a cold dormant period within USDA 7-10 (overwinters); grown as an annual or biennial in zones 2-11, but a wet cold root zone is more dangerous than cold air.
What humidity does curly kale need?
Curly Kale prefers about 50-70% relative humidity. Adaptable to outdoor humidity; good airflow matters more than the level itself. Still, humid, crowded plantings encourage powdery mildew, downy mildew and aphid build-up, so space plants well.
How do I raise humidity for curly kale?
Group it with other plants, stand the pot on a tray of damp pebbles (kept above the waterline), or run a small humidifier in winter. Misting only helps for a few minutes, so it is the weakest option for a plant that genuinely needs more humidity.
Can curly kale live outside?
Curly Kale is rated for USDA zone 7-10 (overwinters); grown as an annual or biennial in zones 2-11 and RHS hardiness H5. Within that range it can stay outdoors; outside it, grow it in a moveable container and protect the roots from a wet, cold winter.
More curly kale care
In the UK? Keeping curly kale warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full curly kale care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.