Plant care
South African Geraniumtemperature & humidity
Pelargonium sidoides
More about south african geranium
Ideal temperature for south african geranium
Temperature kills fewer south african geranium 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 5-28°C (41-82°F) is fine; the spot you put the plant in matters more. Below roughly 5°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
South African Geranium is comparatively hardy (USDA 8-10 (tuberous roots may survive light frost if dry), RHS H3). 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 south african geranium
South African Geranium sits happiest at around 30-50% relative humidity. Prefers low to moderate humidity; high humidity, especially in winter, promotes botrytis and stem rot. Keep indoors or under cover during cold, damp months with good ventilation. 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.
South African Geranium temperature & humidity — frequently asked questions
What temperature is best for south african geranium?
South African Geranium grows best between 5-28°C (41-82°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 south african geranium tolerate?
South African Geranium starts to suffer below roughly 5°C. It tolerates a cold dormant period within USDA 8-10 (tuberous roots may survive light frost if dry), but a wet cold root zone is more dangerous than cold air.
What humidity does south african geranium need?
South African Geranium prefers about 30-50% relative humidity. Prefers low to moderate humidity; high humidity, especially in winter, promotes botrytis and stem rot. Keep indoors or under cover during cold, damp months with good ventilation.
How do I raise humidity for south african geranium?
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 south african geranium live outside?
South African Geranium is rated for USDA zone 8-10 (tuberous roots may survive light frost if dry) and RHS hardiness H3. 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 south african geranium care
In the UK? Keeping south african geranium warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full south african geranium care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.