Plant care
giant reed grasstemperature & humidity
Arundo donax
More about giant reed grass
Ideal temperature for giant reed grass
giant reed grass is comfortable in any room a person is comfortable in, roughly -15°C to 45°C (top growth killed by hard frost; rhizomes survive to around -20°C) (5°F to 113°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 -15°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
giant reed grass is comparatively hardy (USDA 6–10, RHS H4). 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 giant reed grass
giant reed grass sits happiest at around Low to high (30–90% RH) relative humidity. Native to Mediterranean and subtropical climates, highly tolerant of a broad humidity range. Grows vigorously in humid subtropical conditions and equally well in dry Mediterranean climates provided water is available at the roots. No atmospheric humidity management is required — root-zone moisture availability is the primary driver of growth. 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.
giant reed grass temperature & humidity — frequently asked questions
What temperature is best for giant reed grass?
giant reed grass grows best between -15°C to 45°C (top growth killed by hard frost; rhizomes survive to around -20°C) (5°F to 113°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 giant reed grass tolerate?
giant reed grass starts to suffer below roughly -15°C. It tolerates a cold dormant period within USDA 6–10, but a wet cold root zone is more dangerous than cold air.
What humidity does giant reed grass need?
giant reed grass prefers about Low to high (30–90% RH) relative humidity. Native to Mediterranean and subtropical climates, highly tolerant of a broad humidity range. Grows vigorously in humid subtropical conditions and equally well in dry Mediterranean climates provided water is available at the roots. No atmospheric humidity management is required — root-zone moisture availability is the primary driver of growth.
How do I raise humidity for giant reed grass?
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 giant reed grass live outside?
giant reed grass is rated for USDA zone 6–10 and RHS hardiness H4. 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 giant reed grass care
In the UK? Keeping giant reed grass warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full giant reed grass care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.