Plant care
Roselletemperature & humidity
Hibiscus sabdariffa
More about roselle
Ideal temperature for roselle
Roselle is comfortable in any room a person is comfortable in, roughly 18°C to 35°C (64°F to 95°F) (64°F to 95°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 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Roselle is frost-tender (USDA 9-11, 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 roselle
Roselle sits happiest at around 60–80% RH relative humidity. Prefers warm, humid tropical and subtropical conditions. In cooler or drier temperate climates, grows successfully in polytunnels or greenhouses where humidity and temperature can be maintained. Outdoor crops succeed as summer annuals in USDA Zones 8–11 and in sheltered UK growing sites. 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.
Roselle temperature & humidity — frequently asked questions
What temperature is best for roselle?
Roselle grows best between 18°C to 35°C (64°F to 95°F) (64°F to 95°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 roselle tolerate?
Roselle starts to suffer below roughly 18°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 roselle need?
Roselle prefers about 60–80% RH relative humidity. Prefers warm, humid tropical and subtropical conditions. In cooler or drier temperate climates, grows successfully in polytunnels or greenhouses where humidity and temperature can be maintained. Outdoor crops succeed as summer annuals in USDA Zones 8–11 and in sheltered UK growing sites.
How do I raise humidity for roselle?
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 roselle live outside?
Roselle is rated for USDA zone 9-11 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 roselle care
In the UK? Keeping roselle warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full roselle care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.