Plant care
Scarlet Kaletemperature & humidity
Brassica oleracea var. sabellica 'Scarlet'
More about scarlet kale
Ideal temperature for scarlet kale
Scarlet Kale is comfortable in any room a person is comfortable in, roughly 7-24°C (45-75°F). The mistakes are micro-climates: a north-facing window on a frosty night, a south-facing windowsill in a summer heatwave, the standing draught between an opened kitchen door and the radiator behind it. Read the room around the plant, not the thermostat. Below roughly 7°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Scarlet Kale is comparatively hardy (USDA 7-9 (overwinters; grown as a cool-season annual in colder zones), RHS H4). 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 scarlet kale
Scarlet Kale sits happiest at around Outdoor ambient relative humidity. An outdoor crop with no specific humidity needs; ample spacing keeps the curled foliage dry and discourages aphids and mildew. 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.
Scarlet Kale temperature & humidity — frequently asked questions
What temperature is best for scarlet kale?
Scarlet 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 scarlet kale tolerate?
Scarlet Kale starts to suffer below roughly 7°C. It tolerates a cold dormant period within USDA 7-9 (overwinters; grown as a cool-season annual in colder zones), but a wet cold root zone is more dangerous than cold air.
What humidity does scarlet kale need?
Scarlet Kale prefers about Outdoor ambient relative humidity. An outdoor crop with no specific humidity needs; ample spacing keeps the curled foliage dry and discourages aphids and mildew.
How do I raise humidity for scarlet 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 scarlet kale live outside?
Scarlet Kale is rated for USDA zone 7-9 (overwinters; grown as a cool-season annual in colder zones) and RHS hardiness H4. 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 scarlet kale care
In the UK? Keeping scarlet 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 scarlet kale care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.