Plant care
English Walnut 'Howard'temperature & humidity
Juglans regia 'Howard'
More about english walnut 'howard'
Ideal temperature for english walnut 'howard'
English Walnut 'Howard' is comfortable in any room a person is comfortable in, roughly -23 to 38°C (-9 to 100°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 -23°C growth pauses; cold beyond that pushes it into dormancy rather than killing it outright.
Cold tolerance & winter care
English Walnut 'Howard' is comparatively hardy (USDA 5-9 (commercial crops best in zones 7-9), RHS H5). 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 english walnut 'howard'
English Walnut 'Howard' sits happiest at around Ambient outdoor relative humidity. An outdoor orchard tree; ambient humidity is fine. Hot, humid, wet springs raise walnut blight (Xanthomonas) risk, so late-leafing types like 'Howard' and good airflow help reduce infection. 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.
English Walnut 'Howard' temperature & humidity — frequently asked questions
What temperature is best for english walnut 'howard'?
English Walnut 'Howard' grows best between -23 to 38°C (-9 to 100°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 english walnut 'howard' tolerate?
English Walnut 'Howard' starts to suffer below roughly -23°C. It tolerates a cold dormant period within USDA 5-9 (commercial crops best in zones 7-9), but a wet cold root zone is more dangerous than cold air.
What humidity does english walnut 'howard' need?
English Walnut 'Howard' prefers about Ambient outdoor relative humidity. An outdoor orchard tree; ambient humidity is fine. Hot, humid, wet springs raise walnut blight (Xanthomonas) risk, so late-leafing types like 'Howard' and good airflow help reduce infection.
How do I raise humidity for english walnut 'howard'?
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 english walnut 'howard' live outside?
English Walnut 'Howard' is rated for USDA zone 5-9 (commercial crops best in zones 7-9) and RHS hardiness H5. 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 english walnut 'howard' care
In the UK? Keeping english walnut 'howard' warm in a UK home covers the radiator, single-glazing and heating-season humidity angle. Temperature and humidity are one piece. See the full english walnut 'howard' care guide, its cold-hardiness guide, and watering schedule — humidity and watering problems are easy to confuse.