Plant care
Johnston's Cyrtospermatemperature & humidity
Cyrtosperma johnstonii
More about johnston's cyrtosperma
Ideal temperature for johnston's cyrtosperma
Johnston's Cyrtosperma is comfortable in any room a person is comfortable in, roughly 22–34°C (72–93°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 22°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Johnston's Cyrtosperma is frost-tender (USDA 11–12, RHS H1a). 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 johnston's cyrtosperma
Johnston's Cyrtosperma sits happiest at around 75–95% relative humidity. Requires very high humidity throughout the year as a tropical lowland swamp species. Best grown in a warm, humid greenhouse or tropical growing space. Misting alone is insufficient — sustained ambient humidity above 70% is necessary for healthy leaf development. 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.
Johnston's Cyrtosperma temperature & humidity — frequently asked questions
What temperature is best for johnston's cyrtosperma?
Johnston's Cyrtosperma grows best between 22–34°C (72–93°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 johnston's cyrtosperma tolerate?
Johnston's Cyrtosperma starts to suffer below roughly 22°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 johnston's cyrtosperma need?
Johnston's Cyrtosperma prefers about 75–95% relative humidity. Requires very high humidity throughout the year as a tropical lowland swamp species. Best grown in a warm, humid greenhouse or tropical growing space. Misting alone is insufficient — sustained ambient humidity above 70% is necessary for healthy leaf development.
How do I raise humidity for johnston's cyrtosperma?
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 johnston's cyrtosperma live outside?
Johnston's Cyrtosperma is rated for USDA zone 11–12 and RHS hardiness H1a. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More johnston's cyrtosperma care
In the UK? Keeping johnston's cyrtosperma warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full johnston's cyrtosperma care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.