Plant care
Common Water Starworttemperature & humidity
Callitriche stagnalis
More about common water starwort
Ideal temperature for common water starwort
Temperature kills fewer common water starwort 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 0°C to 22°C (32°F to 72°F) is fine; the spot you put the plant in matters more. Below roughly 0°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Common Water Starwort is comparatively hardy (USDA 4-9, 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 common water starwort
Common Water Starwort sits happiest at around Aquatic — 100% water immersion relative humidity. An entirely aquatic species requiring permanent water contact; when grown in a pond no humidity management is needed, but in an indoor aquarium maintain water temperature between 10–20°C (50–68°F). 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.
Common Water Starwort temperature & humidity — frequently asked questions
What temperature is best for common water starwort?
Common Water Starwort grows best between 0°C to 22°C (32°F to 72°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 common water starwort tolerate?
Common Water Starwort starts to suffer below roughly 0°C. It tolerates a cold dormant period within USDA 4-9, but a wet cold root zone is more dangerous than cold air.
What humidity does common water starwort need?
Common Water Starwort prefers about Aquatic — 100% water immersion relative humidity. An entirely aquatic species requiring permanent water contact; when grown in a pond no humidity management is needed, but in an indoor aquarium maintain water temperature between 10–20°C (50–68°F).
How do I raise humidity for common water starwort?
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 common water starwort live outside?
Common Water Starwort is rated for USDA zone 4-9 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 common water starwort care
In the UK? Keeping common water starwort warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full common water starwort care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.