Plant care
Heart-leaved Blechnumtemperature & humidity
Blechnum cordatum
More about heart-leaved blechnum
Ideal temperature for heart-leaved blechnum
Temperature kills fewer heart-leaved blechnum 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 8–22 °C (46–72 °F) is fine; the spot you put the plant in matters more. Below roughly 8°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Heart-leaved Blechnum is comparatively hardy (USDA 8–10, RHS H3). 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 heart-leaved blechnum
Heart-leaved Blechnum sits happiest at around 55–80% relative humidity. Requires moderate to high humidity. In centrally heated homes, use a pebble tray with water or a humidifier. Although more tolerant of cooler, damper conditions than tropical ferns, low humidity in heated rooms causes tip browning. Good air circulation prevents fungal issues. 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.
Heart-leaved Blechnum temperature & humidity — frequently asked questions
What temperature is best for heart-leaved blechnum?
Heart-leaved Blechnum grows best between 8–22 °C (46–72 °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 heart-leaved blechnum tolerate?
Heart-leaved Blechnum starts to suffer below roughly 8°C. It tolerates a cold dormant period within USDA 8–10, but a wet cold root zone is more dangerous than cold air.
What humidity does heart-leaved blechnum need?
Heart-leaved Blechnum prefers about 55–80% relative humidity. Requires moderate to high humidity. In centrally heated homes, use a pebble tray with water or a humidifier. Although more tolerant of cooler, damper conditions than tropical ferns, low humidity in heated rooms causes tip browning. Good air circulation prevents fungal issues.
How do I raise humidity for heart-leaved blechnum?
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 heart-leaved blechnum live outside?
Heart-leaved Blechnum is rated for USDA zone 8–10 and RHS hardiness H3. 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 heart-leaved blechnum care
In the UK? Keeping heart-leaved blechnum warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full heart-leaved blechnum care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.