Plant care
Stinking Iristemperature & humidity
Iris foetidissima
More about stinking iris
Ideal temperature for stinking iris
Stinking Iris is comfortable in any room a person is comfortable in, roughly -20°C to 30°C; leaves may be damaged below -10°C (-4°F to 86°F; leaves vulnerable below 14°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 -20°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Stinking Iris is comparatively hardy (USDA 6-9, RHS H6). Within that range it tolerates a cold dormant spell outdoors; outside it, grow it in a container you can move under cover or overwinter in a cool but frost-free spot. Hardiness assumes an established plant in well-drained soil — a wet, cold root zone kills far more plants than cold air alone.
Humidity for stinking iris
Stinking Iris sits happiest at around Moderate — 40–70% relative humidity. Tolerates the range of humidity found in temperate garden settings, including the damp conditions of shaded corners. Good air circulation reduces the risk of grey mould on foliage. 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.
Stinking Iris temperature & humidity — frequently asked questions
What temperature is best for stinking iris?
Stinking Iris grows best between -20°C to 30°C; leaves may be damaged below -10°C (-4°F to 86°F; leaves vulnerable below 14°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 stinking iris tolerate?
Stinking Iris starts to suffer below roughly -20°C. It tolerates a cold dormant period within USDA 6-9, but a wet cold root zone is more dangerous than cold air.
What humidity does stinking iris need?
Stinking Iris prefers about Moderate — 40–70% relative humidity. Tolerates the range of humidity found in temperate garden settings, including the damp conditions of shaded corners. Good air circulation reduces the risk of grey mould on foliage.
How do I raise humidity for stinking iris?
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 stinking iris live outside?
Stinking Iris is rated for USDA zone 6-9 and RHS hardiness H6. Within that range it can stay outdoors; outside it, grow it in a moveable container and protect the roots from a wet, cold winter.
More stinking iris care
In the UK? Keeping stinking iris warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full stinking iris care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.