Plant care
Large Bitter-cresstemperature & humidity
Cardamine amara
More about large bitter-cress
Ideal temperature for large bitter-cress
Temperature kills fewer large bitter-cress 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 -15°C to 22°C (5°F to 72°F) is fine; the spot you put the plant in matters more. Below roughly -15°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Large Bitter-cress is comparatively hardy (USDA 4-7, RHS H5). 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 large bitter-cress
Large Bitter-cress sits happiest at around High relative humidity. Naturally found in humid riparian environments; in drier garden settings, position near a water feature and mulch heavily to retain moisture. 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.
Large Bitter-cress temperature & humidity — frequently asked questions
What temperature is best for large bitter-cress?
Large Bitter-cress grows best between -15°C to 22°C (5°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 large bitter-cress tolerate?
Large Bitter-cress starts to suffer below roughly -15°C. It tolerates a cold dormant period within USDA 4-7, but a wet cold root zone is more dangerous than cold air.
What humidity does large bitter-cress need?
Large Bitter-cress prefers about High relative humidity. Naturally found in humid riparian environments; in drier garden settings, position near a water feature and mulch heavily to retain moisture.
How do I raise humidity for large bitter-cress?
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 large bitter-cress live outside?
Large Bitter-cress is rated for USDA zone 4-7 and RHS hardiness H5. 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 large bitter-cress care
In the UK? Keeping large bitter-cress warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full large bitter-cress care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.