Plant care
Emerald Spike Mosstemperature & humidity
Selaginella martensii
More about emerald spike moss
Ideal temperature for emerald spike moss
Emerald Spike Moss is comfortable in any room a person is comfortable in, roughly 18-24°C (65-75°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 18°C the damage starts — soft blackened patches, translucent leaves, sometimes overnight.
Cold tolerance & winter care
Emerald Spike Moss is frost-tender (USDA 9-11 (grown indoors / under glass in most US and UK homes), RHS undefined). It cannot survive a frost, so in most of the US and UK it lives indoors year-round or summers outside and comes back in well before the first autumn frost — once nights drop toward 10-12°C is the cue, not the first frost warning. Acclimate it over a week when moving between indoors and out so the leaves do not shock.
Humidity for emerald spike moss
Emerald Spike Moss sits happiest at around 60-80%+ relative humidity. High humidity is non-negotiable — this is the single hardest part of its care. Below about 50% the fine foliage browns and crisps quickly. A closed or open terrarium, propagation case, or grouping with a humidifier is strongly recommended over an open shelf. 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.
Emerald Spike Moss temperature & humidity — frequently asked questions
What temperature is best for emerald spike moss?
Emerald Spike Moss grows best between 18-24°C (65-75°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 emerald spike moss tolerate?
Emerald Spike Moss starts to suffer below roughly 18°C. It is frost-tender and will be damaged or killed by a frost, so bring it indoors once nights fall toward 10-12°C.
What humidity does emerald spike moss need?
Emerald Spike Moss prefers about 60-80%+ relative humidity. High humidity is non-negotiable — this is the single hardest part of its care. Below about 50% the fine foliage browns and crisps quickly. A closed or open terrarium, propagation case, or grouping with a humidifier is strongly recommended over an open shelf.
How do I raise humidity for emerald spike moss?
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 emerald spike moss live outside?
Emerald Spike Moss is rated for USDA zone 9-11 (grown indoors / under glass in most US and UK homes). Outside that range it must come indoors before the first frost — treat any outdoor stint as a summer holiday, not a permanent home.
More emerald spike moss care
In the UK? Keeping emerald spike moss warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full emerald spike moss care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.