Plant care
Emerald Green Arborvitaetemperature & humidity
Thuja occidentalis 'Smaragd'
More about emerald green arborvitae
Ideal temperature for emerald green arborvitae
Emerald Green Arborvitae is comfortable in any room a person is comfortable in, roughly -37 to 32°C (-35 to 90°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 -37°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Emerald Green Arborvitae is comparatively hardy (USDA 3-8 (popular cold-hardy hedge), 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 emerald green arborvitae
Emerald Green Arborvitae sits happiest at around Ambient outdoor humidity relative humidity. An outdoor hedging conifer unaffected by humidity; good airflow between plants reduces fungal needle blight in humid regions. 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.
Emerald Green Arborvitae temperature & humidity — frequently asked questions
What temperature is best for emerald green arborvitae?
Emerald Green Arborvitae grows best between -37 to 32°C (-35 to 90°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 emerald green arborvitae tolerate?
Emerald Green Arborvitae starts to suffer below roughly -37°C. It tolerates a cold dormant period within USDA 3-8 (popular cold-hardy hedge), but a wet cold root zone is more dangerous than cold air.
What humidity does emerald green arborvitae need?
Emerald Green Arborvitae prefers about Ambient outdoor humidity relative humidity. An outdoor hedging conifer unaffected by humidity; good airflow between plants reduces fungal needle blight in humid regions.
How do I raise humidity for emerald green arborvitae?
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 emerald green arborvitae live outside?
Emerald Green Arborvitae is rated for USDA zone 3-8 (popular cold-hardy hedge) 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 emerald green arborvitae care
In the UK? Keeping emerald green arborvitae warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full emerald green arborvitae care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.