UK temperature
Keeping long-leaved pelargonium warm in a UK home
Pelargonium longifolium
More about long-leaved pelargonium in the UK
The UK home, in plant terms
A typical UK home creates two opposite micro-problems at the same time. Radiator-driven heating spikes the air temperature and crashes humidity in the rooms where people actually sit; the older the housing stock the more likely a single-glazed window pane is sitting at near-freezing in January with a houseplant against it. Cold unheated bedrooms, north-facing rooms and conservatories without heating run far cooler than the thermostat suggests, and the British winter gives the lowest indoor daylight in any of Growli's markets. Long-leaved Pelargonium is frost-tender, so the radiator-warmed side of the house is right for it in winter — just not pressed against a cold pane or directly in the radiator updraft.
The actual numbers
Ideally long-leaved pelargonium sits between 7–24°C. (That is 45–75°F in Fahrenheit.) 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. Watch for the room dropping below about 7°C overnight — common in UK unheated bedrooms in January, and the point where growth stalls and leaves chill-mark.
For the RHS hardiness side of this, see is long-leaved pelargonium hardy in the UK? (rating RHS H2, sourced from the RHS rating system). For the US/USDA framing of the same numbers, see the long-leaved pelargonium temperature guide.
Winter placement in a UK home
For long-leaved pelargonium through a UK winter, three placement rules clear up most problems: 1) keep it at least a hand's width back from the window pane on single-glazed or very cold double-glazed glass, especially overnight when curtains close behind the plant; 2) keep it out of the direct vertical updraft above a radiator — that column of hot dry air browns leaf tips even on tolerant species; 3) judge by the room you can actually feel, not the central thermostat — many UK rooms run several degrees below the hall reading in winter. Humidity drops to roughly 25–35% in a heated UK living room; a pebble tray, grouping with other plants, or a small humidifier puts that back to a level houseplants actually like.
Long-leaved Pelargonium temperature in the UK — frequently asked questions
What temperature does long-leaved pelargonium need in the UK?
Long-leaved Pelargonium prefers 7–24°C (45–75°F). The British issue is rarely the average — it is the extremes: a cold single-glazed window in January, the hot dry air directly above a radiator, or a north-facing unheated room that runs far cooler than the hall thermostat.
Will long-leaved pelargonium survive a cold UK winter room?
Long-leaved Pelargonium is frost-tender (RHS H2). Keep it well above freezing, ideally above 10°C overnight, which means the radiator-warmed side of the house rather than an unheated bedroom or conservatory.
Can long-leaved pelargonium go on a UK windowsill in winter?
On a single-glazed or very cold pane, no — overnight the leaves pressed against the glass can drop below the plant's comfort band, especially behind drawn curtains. A small gap (a hand's width back) or thicker thermal curtains in front of the plant fixes it, and modern double-glazing usually solves it outright.
Does UK radiator-driven heating dry long-leaved pelargonium out?
Yes — UK living rooms typically run at around 25–35% relative humidity in winter. That is well below what most houseplants prefer. Long-leaved Pelargonium tolerates this better than the calathea-and-fern family, but a pebble tray or grouping plants still helps.
What temperature range does long-leaved pelargonium actually like?
7–24°C is the comfortable band (45–75°F in Fahrenheit for reference). That covers normal UK living-room temperatures all year; the work is making sure cold pockets (windowsills, unheated rooms) and hot pockets (radiator updrafts) do not push it outside that band.
More long-leaved pelargonium care
See the full long-leaved pelargonium care guide, its UK watering (hard vs soft tap water), and UK hardiness.