Plant care
Giant Arrowheadtemperature & humidity
Sagittaria montevidensis
More about giant arrowhead
Ideal temperature for giant arrowhead
Giant Arrowhead is comfortable in any room a person is comfortable in, roughly 15–35 °C (active growth); plants die back below 10 °C; in frost-prone areas treat as an annual or overwinter containers indoors (59–95 °F (active growth); dies back below 50 °F; overwinter indoors in frost-prone climates). 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 Arrowhead is comparatively hardy (USDA 7-11, RHS H3). 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 arrowhead
Giant Arrowhead sits happiest at around High (pond surface environment) relative humidity. No supplemental humidity required in outdoor cultivation; the emergent habit places foliage in ambient outdoor humidity which is adequate. 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 Arrowhead temperature & humidity — frequently asked questions
What temperature is best for giant arrowhead?
Giant Arrowhead grows best between 15–35 °C (active growth); plants die back below 10 °C; in frost-prone areas treat as an annual or overwinter containers indoors (59–95 °F (active growth); dies back below 50 °F; overwinter indoors in frost-prone climates). 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 arrowhead tolerate?
Giant Arrowhead starts to suffer below roughly 15°C. It tolerates a cold dormant period within USDA 7-11, but a wet cold root zone is more dangerous than cold air.
What humidity does giant arrowhead need?
Giant Arrowhead prefers about High (pond surface environment) relative humidity. No supplemental humidity required in outdoor cultivation; the emergent habit places foliage in ambient outdoor humidity which is adequate.
How do I raise humidity for giant arrowhead?
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 arrowhead live outside?
Giant Arrowhead is rated for USDA zone 7-11 and RHS hardiness H3. 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 arrowhead care
In the UK? Keeping giant arrowhead 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 arrowhead care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.