Plant care
Wilson's Filmy Ferntemperature & humidity
Hymenophyllum wilsonii
More about wilson's filmy fern
Ideal temperature for wilson's filmy fern
Temperature kills fewer wilson's filmy fern 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 4–14°C (39–57°F) is fine; the spot you put the plant in matters more. Below roughly 4°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Wilson's Filmy Fern is comparatively hardy (USDA 7-9, RHS H6). 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 wilson's filmy fern
Wilson's Filmy Fern sits happiest at around 90–100% relative humidity. A sealed terrarium or Wardian case is the only reliable way to maintain the humidity this species requires. In its native upland habitats, humidity rarely falls below 90% even in summer. A fall below 80% for even a few hours is sufficient to kill exposed fronds. 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.
Wilson's Filmy Fern temperature & humidity — frequently asked questions
What temperature is best for wilson's filmy fern?
Wilson's Filmy Fern grows best between 4–14°C (39–57°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 wilson's filmy fern tolerate?
Wilson's Filmy Fern starts to suffer below roughly 4°C. It tolerates a cold dormant period within USDA 7-9, but a wet cold root zone is more dangerous than cold air.
What humidity does wilson's filmy fern need?
Wilson's Filmy Fern prefers about 90–100% relative humidity. A sealed terrarium or Wardian case is the only reliable way to maintain the humidity this species requires. In its native upland habitats, humidity rarely falls below 90% even in summer. A fall below 80% for even a few hours is sufficient to kill exposed fronds.
How do I raise humidity for wilson's filmy fern?
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 wilson's filmy fern live outside?
Wilson's Filmy Fern is rated for USDA zone 7-9 and RHS hardiness H6. 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 wilson's filmy fern care
In the UK? Keeping wilson's filmy fern warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full wilson's filmy fern care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.