Plant care
Savoy Cabbagetemperature & humidity
Brassica oleracea var. sabauda 'Savoy King'
More about savoy cabbage
Ideal temperature for savoy cabbage
Temperature kills fewer savoy cabbage plants than you'd think. What kills them is the micro-climate within a normal-temperature room — a leaf pressed against single-glazed winter glass, the hot dry updraft directly above a radiator, the cold blast from an AC vent. The thermostat reading at 7-24°C (45-75°F) is fine; the spot you put the plant in matters more. Below roughly 7°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Savoy Cabbage is comparatively hardy (USDA 6-9 (overwinters); grown as an annual or biennial in zones 1-9, 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 savoy cabbage
Savoy Cabbage sits happiest at around 50-70% relative humidity. Handles outdoor humidity well; ventilation is key. Tight, humid plantings encourage downy mildew, grey mould in the heads, and aphids, so space plants for airflow and avoid wetting the developing hearts. 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.
Savoy Cabbage temperature & humidity — frequently asked questions
What temperature is best for savoy cabbage?
Savoy Cabbage 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 savoy cabbage tolerate?
Savoy Cabbage starts to suffer below roughly 7°C. It tolerates a cold dormant period within USDA 6-9 (overwinters); grown as an annual or biennial in zones 1-9, but a wet cold root zone is more dangerous than cold air.
What humidity does savoy cabbage need?
Savoy Cabbage prefers about 50-70% relative humidity. Handles outdoor humidity well; ventilation is key. Tight, humid plantings encourage downy mildew, grey mould in the heads, and aphids, so space plants for airflow and avoid wetting the developing hearts.
How do I raise humidity for savoy cabbage?
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 savoy cabbage live outside?
Savoy Cabbage is rated for USDA zone 6-9 (overwinters); grown as an annual or biennial in zones 1-9 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 savoy cabbage care
In the UK? Keeping savoy cabbage warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full savoy cabbage care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.