Plant care
Spencer Mixed sweet peatemperature & humidity
Lathyrus odoratus 'Spencer Mixed'
More about spencer mixed sweet pea
Ideal temperature for spencer mixed sweet pea
Temperature kills fewer spencer mixed sweet pea 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 7–20°C (45–68°F) is fine; the spot you put the plant in matters more. Below roughly 7°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Spencer Mixed sweet pea is comparatively hardy (USDA Annual in zones 2–11; best in cool-season windows, 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 spencer mixed sweet pea
Spencer Mixed sweet pea sits happiest at around 50–70% relative humidity. Performs best in moderate humidity with good air circulation. High humidity combined with warmth promotes powdery mildew. Avoid planting in sheltered, airless spots. In hot, dry summers, provide afternoon shade and extra watering to delay decline. 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.
Spencer Mixed sweet pea temperature & humidity — frequently asked questions
What temperature is best for spencer mixed sweet pea?
Spencer Mixed sweet pea grows best between 7–20°C (45–68°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 spencer mixed sweet pea tolerate?
Spencer Mixed sweet pea starts to suffer below roughly 7°C. It tolerates a cold dormant period within USDA Annual in zones 2–11; best in cool-season windows, but a wet cold root zone is more dangerous than cold air.
What humidity does spencer mixed sweet pea need?
Spencer Mixed sweet pea prefers about 50–70% relative humidity. Performs best in moderate humidity with good air circulation. High humidity combined with warmth promotes powdery mildew. Avoid planting in sheltered, airless spots. In hot, dry summers, provide afternoon shade and extra watering to delay decline.
How do I raise humidity for spencer mixed sweet pea?
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 spencer mixed sweet pea live outside?
Spencer Mixed sweet pea is rated for USDA zone Annual in zones 2–11; best in cool-season windows 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 spencer mixed sweet pea care
In the UK? Keeping spencer mixed sweet pea warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full spencer mixed sweet pea care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.