Plant care
Mondo Grasstemperature & humidity
Ophiopogon japonicus
More about mondo grass
Ideal temperature for mondo grass
Mondo Grass is comfortable in any room a person is comfortable in, roughly 15 to 27°C (59 to 80°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 15°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Mondo Grass is comparatively hardy (USDA 7-11 (outdoor in mild zones; houseplant elsewhere), RHS H4). 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 mondo grass
Mondo Grass sits happiest at around 40-60% relative humidity. Tolerant of average household and outdoor humidity. Higher humidity keeps foliage lush, but it is unfussy; good airflow prevents fungal issues in still, damp conditions. 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.
Mondo Grass temperature & humidity — frequently asked questions
What temperature is best for mondo grass?
Mondo Grass grows best between 15 to 27°C (59 to 80°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 mondo grass tolerate?
Mondo Grass starts to suffer below roughly 15°C. It tolerates a cold dormant period within USDA 7-11 (outdoor in mild zones; houseplant elsewhere), but a wet cold root zone is more dangerous than cold air.
What humidity does mondo grass need?
Mondo Grass prefers about 40-60% relative humidity. Tolerant of average household and outdoor humidity. Higher humidity keeps foliage lush, but it is unfussy; good airflow prevents fungal issues in still, damp conditions.
How do I raise humidity for mondo grass?
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 mondo grass live outside?
Mondo Grass is rated for USDA zone 7-11 (outdoor in mild zones; houseplant elsewhere) and RHS hardiness H4. 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 mondo grass care
In the UK? Keeping mondo grass warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full mondo grass care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.