Plant care
Blue Cycastemperature & humidity
Cycas thouarsii
More about blue cycas
Ideal temperature for blue cycas
Temperature kills fewer blue cycas 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 18-30C; tender, brief lows near -3C scorch leaves (65-86F; tender, brief lows near 25F scorch leaves) is fine; the spot you put the plant in matters more. Below roughly 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Blue Cycas is frost-tender (USDA 9b-11 (very light frost only; indoor/glasshouse in most US/UK), RHS H1c). 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 blue cycas
Blue Cycas sits happiest at around 40-60% relative humidity. Tolerant of average humidity indoors and out. Higher humidity supports lush growth but is not required for a healthy plant. 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.
Blue Cycas temperature & humidity — frequently asked questions
What temperature is best for blue cycas?
Blue Cycas grows best between 18-30C; tender, brief lows near -3C scorch leaves (65-86F; tender, brief lows near 25F scorch leaves). 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 blue cycas tolerate?
Blue Cycas 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 blue cycas need?
Blue Cycas prefers about 40-60% relative humidity. Tolerant of average humidity indoors and out. Higher humidity supports lush growth but is not required for a healthy plant.
How do I raise humidity for blue cycas?
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 blue cycas live outside?
Blue Cycas is rated for USDA zone 9b-11 (very light frost only; indoor/glasshouse in most US/UK) and RHS hardiness H1c. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More blue cycas care
In the UK? Keeping blue cycas warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full blue cycas care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.