Plant care
Sweet Pea 'Spencer'temperature & humidity
Lathyrus odoratus 'Spencer'
More about sweet pea 'spencer'
Ideal temperature for sweet pea 'spencer'
Sweet Pea 'Spencer' is comfortable in any room a person is comfortable in, roughly 10-18°C (50-65°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 10°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
Sweet Pea 'Spencer' is comparatively hardy (USDA 2-11 (grown as a cool-season annual), 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 sweet pea 'spencer'
Sweet Pea 'Spencer' sits happiest at around 40-60% relative humidity. Outdoor ambient humidity suits them. Good spacing and airflow reduce powdery mildew on the dense exhibition foliage. 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.
Sweet Pea 'Spencer' temperature & humidity — frequently asked questions
What temperature is best for sweet pea 'spencer'?
Sweet Pea 'Spencer' grows best between 10-18°C (50-65°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 sweet pea 'spencer' tolerate?
Sweet Pea 'Spencer' starts to suffer below roughly 10°C. It tolerates a cold dormant period within USDA 2-11 (grown as a cool-season annual), but a wet cold root zone is more dangerous than cold air.
What humidity does sweet pea 'spencer' need?
Sweet Pea 'Spencer' prefers about 40-60% relative humidity. Outdoor ambient humidity suits them. Good spacing and airflow reduce powdery mildew on the dense exhibition foliage.
How do I raise humidity for sweet pea 'spencer'?
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 sweet pea 'spencer' live outside?
Sweet Pea 'Spencer' is rated for USDA zone 2-11 (grown as a cool-season annual) 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 sweet pea 'spencer' care
In the UK? Keeping sweet pea 'spencer' warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full sweet pea 'spencer' care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.