UK temperature
Keeping black-stemmed spleenwort warm in a UK home
Asplenium resiliens
More about black-stemmed spleenwort 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. Black-stemmed Spleenwort tolerates a wider band, but the worst-case UK winter placement (a cold single-glazed pane plus a hot dry radiator below it) still stresses it through repeated drying and chilling.
The actual numbers
Ideally black-stemmed spleenwort sits between -20 to 28 °C. (That is -4 to 82 °F in Fahrenheit.) Appreciates moderate to high humidity but adapts well to ambient garden conditions in shaded, sheltered spots. Indoors, place on a pebble-and-water humidity tray in heated rooms. Watch for the room dropping below about -20°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 black-stemmed spleenwort hardy in the UK? (rating RHS H5, sourced from the RHS rating system). For the US/USDA framing of the same numbers, see the black-stemmed spleenwort temperature guide.
Winter placement in a UK home
For black-stemmed spleenwort 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.
Black-stemmed Spleenwort temperature in the UK — frequently asked questions
What temperature does black-stemmed spleenwort need in the UK?
Black-stemmed Spleenwort prefers -20 to 28 °C (-4 to 82 °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 black-stemmed spleenwort survive a cold UK winter room?
Black-stemmed Spleenwort tolerates a wider winter band — see its RHS rating H5. Below about -20°C growth stalls; cold-wet roots, not cold air, are usually what kills it indoors.
Can black-stemmed spleenwort 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 black-stemmed spleenwort out?
Yes — UK living rooms typically run at around 25–35% relative humidity in winter. That is well below what most houseplants prefer. Black-stemmed Spleenwort tolerates this better than the calathea-and-fern family, but a pebble tray or grouping plants still helps.
What temperature range does black-stemmed spleenwort actually like?
-20 to 28 °C is the comfortable band (-4 to 82 °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 black-stemmed spleenwort care
See the full black-stemmed spleenwort care guide, its UK watering (hard vs soft tap water), and UK hardiness.