Plant care
Flame nasturtiumtemperature & humidity
Tropaeolum speciosum
More about flame nasturtium
Ideal temperature for flame nasturtium
Temperature kills fewer flame nasturtium 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 -12 to 20°C (10–68°F) is fine; the spot you put the plant in matters more. Below roughly -12°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Flame nasturtium is comparatively hardy (USDA 8–10, 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 flame nasturtium
Flame nasturtium sits happiest at around 60–80% relative humidity. Native to moist Chilean rainforest margins; thrives where summers are cool and humid. Performs best in the wetter upland gardens of the UK — northwest England, Wales, Scotland, and Ireland. Struggles in the hot, dry south and east. 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.
Flame nasturtium temperature & humidity — frequently asked questions
What temperature is best for flame nasturtium?
Flame nasturtium grows best between -12 to 20°C (10–68°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 flame nasturtium tolerate?
Flame nasturtium starts to suffer below roughly -12°C. It tolerates a cold dormant period within USDA 8–10, but a wet cold root zone is more dangerous than cold air.
What humidity does flame nasturtium need?
Flame nasturtium prefers about 60–80% relative humidity. Native to moist Chilean rainforest margins; thrives where summers are cool and humid. Performs best in the wetter upland gardens of the UK — northwest England, Wales, Scotland, and Ireland. Struggles in the hot, dry south and east.
How do I raise humidity for flame nasturtium?
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 flame nasturtium live outside?
Flame nasturtium is rated for USDA zone 8–10 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 flame nasturtium care
In the UK? Keeping flame nasturtium warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full flame nasturtium care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.