Plant care
Fishtail Sword Ferntemperature & humidity
Nephrolepis falcata
More about fishtail sword fern
Ideal temperature for fishtail sword fern
Temperature kills fewer fishtail sword 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 18–30°C (64–86°F) is fine; the spot you put the plant in matters more. Below roughly 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Fishtail Sword Fern is frost-tender (USDA 10–12, RHS H1b). It cannot survive a frost, so in most of the US and UK it lives indoors year-round or summers outside and comes back in well before the first autumn frost — once nights drop toward 10-12°C is the cue, not the first frost warning. Acclimate it over a week when moving between indoors and out so the leaves do not shock.
Humidity for fishtail sword fern
Fishtail Sword Fern sits happiest at around 50–70% relative humidity. Prefers moderate to high humidity, especially indoors in heated environments. Pebble trays, plant groupings, or a cool-mist humidifier help maintain suitable levels. In tropical outdoor conditions, ambient humidity is generally sufficient. Low humidity leads to brown frond margins. 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 Sword Fern temperature & humidity — frequently asked questions
What temperature is best for fishtail sword fern?
Fishtail Sword Fern grows best between 18–30°C (64–86°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 sword fern tolerate?
Fishtail Sword Fern starts to suffer below roughly 18°C. It is frost-tender and will be damaged or killed by a frost, so bring it indoors once nights fall toward 10-12°C.
What humidity does fishtail sword fern need?
Fishtail Sword Fern prefers about 50–70% relative humidity. Prefers moderate to high humidity, especially indoors in heated environments. Pebble trays, plant groupings, or a cool-mist humidifier help maintain suitable levels. In tropical outdoor conditions, ambient humidity is generally sufficient. Low humidity leads to brown frond margins.
How do I raise humidity for fishtail sword 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 sword fern live outside?
Fishtail Sword Fern is rated for USDA zone 10–12 and RHS hardiness H1b. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More fishtail sword fern care
In the UK? Keeping fishtail sword 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 sword fern care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.