Gardeners are being urged to rethink where they grow hydrangeas as hotter summers leave the much-loved flowering shrub struggling in parts of the UK. The Royal Horticultural Society (RHS) says prolonged periods of heat and drought are taking their toll on hydrangeas, with the charity even considering relocating part of its own collection from RHS Wisley in Surrey to its northern gardens, where conditions are cooler and wetter.
Hydrangeas, known for their large pink, purple and blue blooms, have long been a staple of British gardens thanks to the country’s traditionally mild and damp climate. However, the RHS says rising temperatures are making it increasingly difficult for some varieties to thrive, particularly in southern England.
Figures from the RHS gardening advice service show enquiries about heat and drought damage affecting hydrangeas have more than tripled since 2023, The Guardian reports. They are now the most commonly reported plant suffering during spells of hot weather.
Guy Barter, the RHS’s chief horticulturist, said: “Hot dry summers are not the best for hydrangeas, although it is mainly the Hydrangea macrophylla types (mophead and lacecaps) that suffer most, especially in sunnier sites and sandy soils such as we have at Wisley.
“However, in light shade, north facing slopes or where the soil is a bit moister, they remain a fantastic plant for summer flowers, especially the more resilient Hydrangea paniculata.
“Our northern gardens have better soils and a superior climate for hydrangeas, hence the shift in emphasis. As the climate changes, bringing hotter drier summers, gardeners, like the RHS, will have to be more selective about where they plant hydrangeas.”
The charity is advising gardeners to move potted hydrangeas into dappled shade during periods of extreme heat and to water them thoroughly rather than little and often. Applying mulch around the base of plants can also help the soil retain moisture.
For hydrangeas growing in the ground, the RHS recommends considering moving them to a cooler, shadier position during the autumn if they are currently planted in full sun.
Tim Upson, the RHS’s director of gardens, said: “We’ve seen first-hand at our gardens that hydrangeas growing in shadier positions cope far better during prolonged hot dry weather than those exposed to full sun and so we will need to think about where we site our hydrangeas at RHS Wisley in the future so we can continue to grow them.
“We encourage gardeners to move potted hydrangeas into dappled shade during extreme heat, water deeply rather than little and often, apply mulch to retain soil moisture and, where necessary, relocate plants growing in the ground in full sun to a cooler, shadier spot in the autumn.”
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