The Royal Horticultural Society (RHS) has issued a warning that hotter summers and heatwaves, including one currently affecting parts of England, are endangering hydrangeas in the south of the country. Historically, these shrubs have thrived in Britain's mild, damp climate.
Data from the RHS gardening advice service indicates that inquiries regarding drought and heat damage to hydrangeas have more than tripled since 2023. This makes them the most frequently reported plant experiencing hot weather problems, rising from seventh place in 2023 to first in 2025 and remaining so in 2026.
The gardening charity is considering relocating its hydrangea collection from its Wisley garden in Surrey to its northern gardens in Great Manchester and North Yorkshire. These northern locations are expected to offer more favourable conditions, being less hot and dry. Guy Barter, chief horticulturist at the RHS, noted that while some types of hydrangeas suffer more, others, like Hydrangea paniculata, are more resilient in suitable conditions.
Tim Upson, RHS director of gardens, advised gardeners to move potted hydrangeas into dappled shade during extreme heat and to water deeply. He also suggested applying mulch to retain soil moisture and, if necessary, relocating ground-planted hydrangeas from full sun to a shadier spot in autumn.