Plant care
Long-leaved Pelargoniumtemperature & humidity
Pelargonium longifolium
More about long-leaved pelargonium
Ideal temperature for long-leaved pelargonium
Temperature kills fewer long-leaved pelargonium 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 7–24°C (45–75°F) is fine; the spot you put the plant in matters more. Below roughly 7°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Long-leaved Pelargonium is frost-tender (USDA 9-11 (overwinter frost-free elsewhere), 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 long-leaved pelargonium
Long-leaved Pelargonium sits happiest at around 30–50% relative humidity. Tolerates low to average humidity and actively benefits from good ventilation. Avoid misting or placing in humid bathrooms; dry air mirrors the plant's native semi-arid habitat and reduces fungal issues. 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.
Long-leaved Pelargonium temperature & humidity — frequently asked questions
What temperature is best for long-leaved pelargonium?
Long-leaved Pelargonium grows best between 7–24°C (45–75°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 long-leaved pelargonium tolerate?
Long-leaved Pelargonium starts to suffer below roughly 7°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 long-leaved pelargonium need?
Long-leaved Pelargonium prefers about 30–50% relative humidity. Tolerates low to average humidity and actively benefits from good ventilation. Avoid misting or placing in humid bathrooms; dry air mirrors the plant's native semi-arid habitat and reduces fungal issues.
How do I raise humidity for long-leaved pelargonium?
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 long-leaved pelargonium live outside?
Long-leaved Pelargonium is rated for USDA zone 9-11 (overwinter frost-free elsewhere) 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 long-leaved pelargonium care
In the UK? Keeping long-leaved pelargonium warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full long-leaved pelargonium care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.