Results from the RHS Extreme Heat Survey revealed which plants across the UK were damaged – with advice for future as scorching summers continue
More than 8,000 people responded to our survey in July 2022, painting a clear picture that even established, formerly healthy plants could not cope with the searing temperatures, which reached well above 30°c across the UK and in some areas hit 40°c.
In 2026, the survey is back. Have your say here and tell us what has struggled, thrived or surprised you in your garden.
The survey’s key findings
The survey asked people questions about plants in their gardens that had suffered damage during the heatwave. These responses give the RHS a broad view of the immediate harm of high temperatures to garden plants and how this might be exacerbated as the climate continues to warm and extreme weather becomes increasingly frequent.
The top 10 plants that suffered the most damage in July 2022 were:
- Hydrangea
- Acer
- Fuchsia
- Astilbe
- Roses
- Anemone
- Ferns
- Heuchera
- Phlox
- Crocosmia
Many of the plants in the top 10 were expected, such as hydrangea, Japanese maple (acers) and hardy fuchsia species, as they prefer cooler conditions with plenty of soil moisture. In addition, these varieties are often planted in dry and exposed sites and this may have contributed to their vulnerability.
However, others such as roses were more of a surprise. Some had flower damage in July and August but many went on to have an extended flowering season and were still producing flowers in late October.
Fans of the fiery-coloured crocosmia will be reassured that the damage to these plants is unlikely to affect them in the long-term. Although their leaves are easily scorched, the damage is often superficial as they are
drought-tolerant plants and are likely to re-emerge.
Magnolia, rhododendron and camellia do not appear in the top 10 despite drought resulting in leaf loss, dieback and often death. Since these had already finished flowering by the summer, damage might have been less obvious. The
RHS Garden Advice Service later looked out for reports of damaged plants in the spring as they come into bloom.
Techniques that would usually protect plants and help them retain water, such as
mulching,
in some cases also proved ineffective against the prolonged heat and drought, according to survey respondents.
With similar summer temperatures becoming more common, gardeners should resist the urge to prune plants that have lost a lot of leaves. Most plants will still have live buds on their stems and branches and will leaf up again when the temperature is right and rain arrives, but pruning after heat and drought can put them under more stress. Come spring, woody plants will show where any dead wood is more clearly, ensuring you can prune the right parts of plants that were affected by the heat in summer.
How to support plants in a changing climate
Leigh Hunt, RHS Principal Horticultural Advisor, said: “As temperatures become more extreme, don’t replace like for like – if a plant is struggling in your garden, you can plant something better suited to the space. Dry gardens don’t have to mean gravel gardens – you can keep an English-style garden by swapping plants, for example exchange rhododendrons for
Grevillea.
“Timing is especially important in the garden, and gardening calendars aren’t as reliable as your own green fingers as seasons become more variable. You can make good use of the longer seasons as many plants including asters and salvias are now providing a brilliant show well into November.”
Right plant, right place
The results highlight the importance of planting in the right place at the right time and being water-wise all year round. Climate-resilient planting can help gardens cope with extremes of temperatures and moisture, as well as ensuring habitats and food for wildlife throughout the year.
While mulching alone does not seem to have protected some plants from such high temperatures, a combination of measures such as improving soil with home compost to ensure it holds more water and harvesting rainwater with water butts to keep plants that require it moist, could help.
Read more
