Plant care
Rex begoniatemperature & humidity
Begonia rex
More about rex begonia
Ideal temperature for rex begonia
Rex begonia is comfortable in any room a person is comfortable in, roughly 16-24°C (60-75°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 16°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Rex begonia is frost-tender (USDA 10-11 (indoor-only), RHS H1b). It cannot survive a frost, so in most of the US and UK it lives indoors year-round or summers outside and comes back in well before the first autumn frost — once nights drop toward 10-12°C is the cue, not the first frost warning. Acclimate it over a week when moving between indoors and out so the leaves do not shock.
Humidity for rex begonia
Rex begonia sits happiest at around 50-70% relative humidity. High humidity keeps the foliage glossy; under 40% leaves crisp at the edges. 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.
Rex begonia temperature & humidity — frequently asked questions
What temperature is best for rex begonia?
Rex begonia grows best between 16-24°C (60-75°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 rex begonia tolerate?
Rex begonia starts to suffer below roughly 16°C. It is frost-tender and will be damaged or killed by a frost, so bring it indoors once nights fall toward 10-12°C.
What humidity does rex begonia need?
Rex begonia prefers about 50-70% relative humidity. High humidity keeps the foliage glossy; under 40% leaves crisp at the edges.
How do I raise humidity for rex begonia?
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 rex begonia live outside?
Rex begonia is rated for USDA zone 10-11 (indoor-only) and RHS hardiness H1b. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More rex begonia care
In the UK? Keeping rex begonia warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full rex begonia care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.