Plant care
Crassula Alstoniitemperature & humidity
Crassula alstonii
More about crassula alstonii
Ideal temperature for crassula alstonii
Aim for 18-26°C (65-79°F) on the thermostat and you've handled the easy part. The hard part is the half-metre around the plant: window glass that drops to near-freezing on a January night, a radiator pumping out hot dry air, a draught from an opened front door. Move the plant 30 cm and you've usually fixed the problem. Below roughly 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Crassula Alstonii is frost-tender (USDA 9b-11 (indoor in most US homes), RHS H2 (tender; keep above about 5-10°C and dry in winter)). 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 crassula alstonii
Crassula Alstonii sits happiest at around 30-40% relative humidity. Prefers dry, well-ventilated air and resents humidity, which lingers in the packed leaves and triggers rot. Never mist it. Steady airflow around the plant is far more valuable than any added moisture, especially during its summer rest. 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.
Crassula Alstonii temperature & humidity — frequently asked questions
What temperature is best for crassula alstonii?
Crassula Alstonii grows best between 18-26°C (65-79°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 crassula alstonii tolerate?
Crassula Alstonii 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 crassula alstonii need?
Crassula Alstonii prefers about 30-40% relative humidity. Prefers dry, well-ventilated air and resents humidity, which lingers in the packed leaves and triggers rot. Never mist it. Steady airflow around the plant is far more valuable than any added moisture, especially during its summer rest.
How do I raise humidity for crassula alstonii?
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 crassula alstonii live outside?
Crassula Alstonii is rated for USDA zone 9b-11 (indoor in most US homes) and RHS hardiness H2 (tender; keep above about 5-10°C and dry in winter). Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More crassula alstonii care
In the UK? Keeping crassula alstonii warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full crassula alstonii care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.