Plant care
Autumn Ferntemperature & humidity
Dryopteris erythrosora
More about autumn fern
Ideal temperature for autumn fern
Temperature kills fewer autumn 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 15-29 C (60-85 F) is fine; the spot you put the plant in matters more. Below roughly 15°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Autumn Fern is comparatively hardy (USDA USDA zones 5-9, RHS undefined). 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 autumn fern
Autumn Fern sits happiest at around 50% or higher relative humidity. Native to cool, shady Asian forests, so it thrives in high humidity. Indoors, group with other plants, sit the pot on a pebble-and-water tray, or run a humidifier. Low humidity from heating or drafts causes brown, brittle frond edges. 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.
Autumn Fern temperature & humidity — frequently asked questions
What temperature is best for autumn fern?
Autumn Fern grows best between 15-29 C (60-85 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 autumn fern tolerate?
Autumn Fern starts to suffer below roughly 15°C. It tolerates a cold dormant period within USDA USDA zones 5-9, but a wet cold root zone is more dangerous than cold air.
What humidity does autumn fern need?
Autumn Fern prefers about 50% or higher relative humidity. Native to cool, shady Asian forests, so it thrives in high humidity. Indoors, group with other plants, sit the pot on a pebble-and-water tray, or run a humidifier. Low humidity from heating or drafts causes brown, brittle frond edges.
How do I raise humidity for autumn 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 autumn fern live outside?
Autumn Fern is rated for USDA zone USDA zones 5-9. 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 autumn fern care
In the UK? Keeping autumn 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 autumn fern care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.