Plant care
Kumquattemperature & humidity
Fortunella japonica
More about kumquat
Ideal temperature for kumquat
Temperature kills fewer kumquat 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 13-30°C (55-86°F) is fine; the spot you put the plant in matters more. Below roughly 13°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Kumquat is frost-tender (USDA 8-11 outdoors (the most cold-tolerant of the common citrus group); container-grown and overwintered indoors in colder zones, RHS H2). 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 kumquat
Kumquat sits happiest at around 40-60% relative humidity. Tolerates average household humidity. In dry, heated winter rooms a humidity boost deters spider mites and bud drop; keep away from radiators and cold drafts. 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.
Kumquat temperature & humidity — frequently asked questions
What temperature is best for kumquat?
Kumquat grows best between 13-30°C (55-86°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 kumquat tolerate?
Kumquat starts to suffer below roughly 13°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 kumquat need?
Kumquat prefers about 40-60% relative humidity. Tolerates average household humidity. In dry, heated winter rooms a humidity boost deters spider mites and bud drop; keep away from radiators and cold drafts.
How do I raise humidity for kumquat?
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 kumquat live outside?
Kumquat is rated for USDA zone 8-11 outdoors (the most cold-tolerant of the common citrus group); container-grown and overwintered indoors in colder zones and RHS hardiness H2. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More kumquat care
In the UK? Keeping kumquat warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full kumquat care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.