The Royal Horticultural Society (RHS) is considering moving its hydrangea collection from Wisley, Surrey, to its northern gardens in Greater Manchester and North Yorkshire due to hotter summers and heatwaves.
Data from the RHS gardening advice service show inquiries about drought and heat damage affecting hydrangeas have more than tripled since 2023, making them the most frequently reported plant for hot weather problems. Hydrangeas rose from seventh to first place between 2023 and 2025 and remain the most reported plant suffering from drought and high temperatures in 2026.
Climate pressures
Guy Barter, chief horticulturist at the RHS, 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.”
He added: “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.”
Northern relocation
At its Manchester garden in Bridgewater, the RHS has conducted a study into hydrangeas and how they are faring in the UK amid climate breakdown. During the 2021-25 trial, the shrubs faced drought and record heat in 2022, heavy rain in 2024 and more hot weather in 2025, damaging the plants and affecting their performance and blooming.
The charity plans to send more plants north, including its prize collection of rhododendrons to Harlow Carr in North Yorkshire, and Wisley's national collections of rhubarb and gooseberries to the Bridgewater garden in Salford.
Adapting to change
Some plants are flourishing, with fig and almond trees doing well in RHS gardens. Banana and lotus have also flowered at Harlow Carr, which was not thought possible 10 years ago.
Tim Upson, the RHS 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.”
He encouraged 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 relocate plants in full sun to a cooler, shadier spot in autumn.
