Plant care
Double King Cuptemperature & humidity
Caltha palustris 'Multiplex'
More about double king cup
Ideal temperature for double king cup
Double King Cup is comfortable in any room a person is comfortable in, roughly -30 to 25°C (-22 to 77°F). The mistakes are micro-climates: a north-facing window on a frosty night, a south-facing windowsill in a summer heatwave, the standing draught between an opened kitchen door and the radiator behind it. Read the room around the plant, not the thermostat. Below roughly -30°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Double King Cup is comparatively hardy (USDA 3-7, RHS H7). 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 double king cup
Double King Cup sits happiest at around High (pond margin and bog garden habitat) relative humidity. Naturally suited to the high-humidity microclimate of pond margins and bog gardens. No supplemental misting needed. Mulching around planting in a bog bed helps maintain a cool, moist environment for the roots and raises local humidity slightly. 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.
Double King Cup temperature & humidity — frequently asked questions
What temperature is best for double king cup?
Double King Cup grows best between -30 to 25°C (-22 to 77°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 double king cup tolerate?
Double King Cup starts to suffer below roughly -30°C. It tolerates a cold dormant period within USDA 3-7, but a wet cold root zone is more dangerous than cold air.
What humidity does double king cup need?
Double King Cup prefers about High (pond margin and bog garden habitat) relative humidity. Naturally suited to the high-humidity microclimate of pond margins and bog gardens. No supplemental misting needed. Mulching around planting in a bog bed helps maintain a cool, moist environment for the roots and raises local humidity slightly.
How do I raise humidity for double king cup?
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 double king cup live outside?
Double King Cup is rated for USDA zone 3-7 and RHS hardiness H7. 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 double king cup care
In the UK? Keeping double king cup warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full double king cup care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.