Plant care
Fishtail Holly Ferntemperature & humidity
Cyrtomium caryotideum
More about fishtail holly fern
Ideal temperature for fishtail holly fern
Temperature kills fewer fishtail holly 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 7–22°C (45–72°F) is fine; the spot you put the plant in matters more. Below roughly 7°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Fishtail Holly Fern is comparatively hardy (USDA 6–10, RHS H5). 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 fishtail holly fern
Fishtail Holly Fern sits happiest at around 40–65% relative humidity. Cyrtomium caryotideum is more tolerant of average household humidity (40–50%) than most ferns, making it an excellent choice for typical living spaces. Frond quality improves above 50%, but brief dry periods are unlikely to cause damage. Mist occasionally in heated rooms. 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.
Fishtail Holly Fern temperature & humidity — frequently asked questions
What temperature is best for fishtail holly fern?
Fishtail Holly Fern grows best between 7–22°C (45–72°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 fishtail holly fern tolerate?
Fishtail Holly Fern starts to suffer below roughly 7°C. It tolerates a cold dormant period within USDA 6–10, but a wet cold root zone is more dangerous than cold air.
What humidity does fishtail holly fern need?
Fishtail Holly Fern prefers about 40–65% relative humidity. Cyrtomium caryotideum is more tolerant of average household humidity (40–50%) than most ferns, making it an excellent choice for typical living spaces. Frond quality improves above 50%, but brief dry periods are unlikely to cause damage. Mist occasionally in heated rooms.
How do I raise humidity for fishtail holly 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 fishtail holly fern live outside?
Fishtail Holly Fern is rated for USDA zone 6–10 and RHS hardiness H5. 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 fishtail holly fern care
In the UK? Keeping fishtail holly 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 fishtail holly fern care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.