Plant care
Mystery Gardeniatemperature & humidity
Gardenia jasminoides 'Mystery'
More about mystery gardenia
Ideal temperature for mystery gardenia
Aim for 16–24 °C day; 13–16 °C night (60–75 °F day; 55–60 °F night) 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 16°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Mystery Gardenia is frost-tender (USDA 8–11, RHS H2). 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 mystery gardenia
Mystery Gardenia sits happiest at around 60–70% relative humidity. High humidity is non-negotiable indoors. Place on a pebble tray partially filled with water (ensuring pot base sits above the waterline), group with other humidity-loving plants, or use a room humidifier. Avoid misting directly onto buds, which can cause brown spotting. 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.
Mystery Gardenia temperature & humidity — frequently asked questions
What temperature is best for mystery gardenia?
Mystery Gardenia grows best between 16–24 °C day; 13–16 °C night (60–75 °F day; 55–60 °F night). 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 mystery gardenia tolerate?
Mystery Gardenia 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 mystery gardenia need?
Mystery Gardenia prefers about 60–70% relative humidity. High humidity is non-negotiable indoors. Place on a pebble tray partially filled with water (ensuring pot base sits above the waterline), group with other humidity-loving plants, or use a room humidifier. Avoid misting directly onto buds, which can cause brown spotting.
How do I raise humidity for mystery gardenia?
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 mystery gardenia live outside?
Mystery Gardenia is rated for USDA zone 8–11 and RHS hardiness H2. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More mystery gardenia care
In the UK? Keeping mystery gardenia warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full mystery gardenia care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.