The Royal Horticultural Society has identified hydrangeas as the plant most vulnerable to heat and drought stress in recent years, reflecting broader shifts in gardening challenges across Britain. Inquiries to the RHS gardening advice service about drought and heat damage to hydrangeas have more than tripled since 2023, with the plant rising from seventh to first place in frequency of reported heat-related problems by 2025 and maintaining that position throughout 2026.
In response to these trends, the RHS is considering a significant reorganization of its plant collections. The organization plans to move its hydrangea collection northward from its Wisley garden in Surrey to its northern facilities in Greater Manchester and North Yorkshire, where climate conditions are projected to remain more suitable for the species. Guy Barter, chief horticulturist at the RHS, explained that certain hydrangea varieties, particularly Hydrangea macrophylla types, struggle most in hot, dry conditions, especially in sunny locations and sandy soils characteristic of the Wisley property. He noted that other species, such as Hydrangea paniculata, demonstrate greater resilience and perform well in partial shade.
A trial conducted at the RHS Manchester garden between 2021 and 2025 tested hydrangea performance under challenging weather conditions, including drought, record heat in 2022, heavy rainfall in 2024, and additional heat in 2025. The results supported the decision to prioritize northern locations. Beyond hydrangeas, the RHS plans to relocate its rhododendron collection to Harlow Carr in North Yorkshire and move its national collections of rhubarb and gooseberries to the Bridgewater garden in Salford.
While some plant species are struggling with climate change, others are thriving in new conditions. Fig and almond trees are performing well in RHS gardens, and tropical species such as bananas and lotus have successfully flowered at Harlow Carr, developments considered unlikely a decade earlier. The RHS has recommended that gardeners protect hydrangeas by positioning them in dappled shade during extreme heat, applying deep watering and mulch, and relocating plants from full sun to shadier locations during autumn months.
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