Plant care
Olympic Mulleintemperature & humidity
Verbascum olympicum
More about olympic mullein
Ideal temperature for olympic mullein
Temperature kills fewer olympic mullein 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 -15 to 38°C (5 to 100°F) is fine; the spot you put the plant in matters more. Below roughly -15°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Olympic Mullein is comparatively hardy (USDA 5–10, RHS H5). 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 olympic mullein
Olympic Mullein sits happiest at around 25–55% relative humidity. Naturally adapted to the low-humidity, arid Mediterranean climate. Performs well in drier temperate climates. The silver-white woolly tomentum on leaves reflects sunlight and reduces moisture loss. Persistent high humidity increases susceptibility to fungal crown rot. 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.
Olympic Mullein temperature & humidity — frequently asked questions
What temperature is best for olympic mullein?
Olympic Mullein grows best between -15 to 38°C (5 to 100°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 olympic mullein tolerate?
Olympic Mullein starts to suffer below roughly -15°C. It tolerates a cold dormant period within USDA 5–10, but a wet cold root zone is more dangerous than cold air.
What humidity does olympic mullein need?
Olympic Mullein prefers about 25–55% relative humidity. Naturally adapted to the low-humidity, arid Mediterranean climate. Performs well in drier temperate climates. The silver-white woolly tomentum on leaves reflects sunlight and reduces moisture loss. Persistent high humidity increases susceptibility to fungal crown rot.
How do I raise humidity for olympic mullein?
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 olympic mullein live outside?
Olympic Mullein is rated for USDA zone 5–10 and RHS hardiness H5. 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 olympic mullein care
In the UK? Keeping olympic mullein warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full olympic mullein care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.