Plant care
Shiso (Perilla)temperature & humidity
Perilla frutescens
More about shiso (perilla)
Ideal temperature for shiso (perilla)
Shiso (Perilla) is comfortable in any room a person is comfortable in, roughly 18-30 C (65-86 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 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Shiso (Perilla) is frost-tender (USDA Perennial only in USDA zones 10a-11b; grown as a frost-tender warm-season annual in all cooler zones, RHS undefined). 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 shiso (perilla)
Shiso (Perilla) sits happiest at around 40-60% (average to slightly high) relative humidity. Shiso enjoys warm, humid summer conditions and average household humidity is fine. In very dry indoor air, raise it occasionally with a pebble tray, but prioritise airflow, since stagnant humid conditions encourage powdery mildew and fungal leaf spot. 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.
Shiso (Perilla) temperature & humidity — frequently asked questions
What temperature is best for shiso (perilla)?
Shiso (Perilla) grows best between 18-30 C (65-86 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 shiso (perilla) tolerate?
Shiso (Perilla) 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 shiso (perilla) need?
Shiso (Perilla) prefers about 40-60% (average to slightly high) relative humidity. Shiso enjoys warm, humid summer conditions and average household humidity is fine. In very dry indoor air, raise it occasionally with a pebble tray, but prioritise airflow, since stagnant humid conditions encourage powdery mildew and fungal leaf spot.
How do I raise humidity for shiso (perilla)?
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 shiso (perilla) live outside?
Shiso (Perilla) is rated for USDA zone Perennial only in USDA zones 10a-11b; grown as a frost-tender warm-season annual in all cooler zones. Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More shiso (perilla) care
In the UK? Keeping shiso (perilla) warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full shiso (perilla) care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.