While everyone is struggling to cope during the 2026 heatwave, spare a thought for trees suffering from heat stress.
The UK is experiencing a particularly dry and hot summer, which is causing problems for many of our native trees. While mature trees are generally regarded as weather-resilient, prolonged dry spells with little or no rainfall can cause heat stress.
If left unchecked, heat stress can weaken a tree, making it more vulnerable to pests, diseases and permanent damage.
Summers are getting hotter
While the weather in Britain is famously unpredictable, the Met Office says there is clear evidence that summer temperatures are rising. Between the years 2015 and 2024, the number of UK days above 30degC more than trebled compared with the average across 1961-1990.
Not surprisingly, the maximum temperature recorded in the UK each year has risen too. Hitting 35degC was rare in the 20th century, but it has been achieved in six of the past 10 years.
To help care for trees, knowing what to look for can help prevent issues such as falling branches. Here are five common signs that a tree is suffering from heat stress…
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Leaves are wilting
One of the earliest signs of heat stress in trees is wilting foliage. Leaves may begin to droop, curl around the edges or appear limp, even when they are still green.
This happens because the tree is trying to conserve moisture. By reducing the surface area exposed to the sun, it loses less water through evaporation. During prolonged hot weather, even established trees can struggle if the ground becomes excessively dry.
If you notice widespread wilting that doesn’t improve after cooler weather or rainfall, it’s worth having the tree assessed.
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Leaves turn brown too early
While it’s perfectly normal for leaves to change colour in autumn, brown or scorched leaves in the middle of summer can be a sign of heat stress. In severe cases, the entire leaf can dry out before falling prematurely.
This is particularly common on younger trees, recently planted specimens and trees growing in exposed locations where they receive full sun throughout the day.
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Excessive leaf drop
Trees sometimes shed a small number of leaves during dry weather as a survival mechanism. However, if large numbers of healthy-looking leaves begin falling during summer, it may indicate that the tree is under considerable heat stress.
By reducing the number of leaves it has to support, the tree requires less water. While this may help it survive temporarily, repeated summers of severe stress can weaken its overall health and reduce future growth. If your lawn suddenly becomes covered in leaves weeks before autumn, it’s worth investigating the cause.
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Cracked soil and dry root zones
The condition of the soil around a tree can tell you just as much as the tree itself. Deep cracks in dry and compacted ground mean water could run off instead of soaking in, suggesting the roots are struggling to access sufficient moisture.
Although mature trees have extensive root systems, prolonged drought can dry out even deeper layers of soil. Young trees, which haven’t yet established wide-reaching roots, are particularly vulnerable.
Applying organic mulch around the base of a tree can help retain moisture, regulate soil temperature and protect the root system during hot weather. Just remember to keep mulch away from direct contact with the trunk.
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Dead branches
One of the more serious signs of heat stress is branch dieback. When a tree cannot supply enough water to all of its branches, it will prioritise its most important areas and allow smaller twigs or outer branches to die back. You may notice brittle branches, sparse foliage or sections of the canopy that fail to produce healthy leaves.
Dead branches don’t just affect the appearance of a tree, they can also become a safety risk if they fall unexpectedly.
Professional pruning can remove damaged growth while allowing the tree to focus its energy on healthy areas.
Worried about trees suffering heat stress?
The good news is that many trees recover well once weather conditions improve, particularly if action is taken early. However, if a tree continues to decline after the weather cools, develops significant deadwood or appears unstable, it’s advisable to seek professional advice.
Here at Branching Out Tree & Garden Services, we are ARB-approved tree surgeons and help keep trees healthy all year round. Whether you’re concerned about heat stress, storm damage, disease or general tree health, our experienced team can make a professional assessment. Contact us today.