Plant care
Sea Lettucetemperature & humidity
Dudleya caespitosa
More about sea lettuce
Ideal temperature for sea lettuce
Sea Lettuce is comfortable in any room a person is comfortable in, roughly 5–25 °C (41–77 °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 5°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Sea Lettuce is comparatively hardy (USDA 9–11, 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 sea lettuce
Sea Lettuce sits happiest at around 30–60% relative humidity. Tolerates typical indoor humidity. Coastal conditions with moderate ambient moisture are natural for this species. Avoid placing near steam sources or in very humid bathrooms; summer wetness is more damaging than winter 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.
Sea Lettuce temperature & humidity — frequently asked questions
What temperature is best for sea lettuce?
Sea Lettuce grows best between 5–25 °C (41–77 °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 sea lettuce tolerate?
Sea Lettuce starts to suffer below roughly 5°C. It tolerates a cold dormant period within USDA 9–11, but a wet cold root zone is more dangerous than cold air.
What humidity does sea lettuce need?
Sea Lettuce prefers about 30–60% relative humidity. Tolerates typical indoor humidity. Coastal conditions with moderate ambient moisture are natural for this species. Avoid placing near steam sources or in very humid bathrooms; summer wetness is more damaging than winter moisture.
How do I raise humidity for sea lettuce?
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 sea lettuce live outside?
Sea Lettuce is rated for USDA zone 9–11 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 sea lettuce care
In the UK? Keeping sea lettuce warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full sea lettuce care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.