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In recent weeks, many people have noticed yellowing leaves and early leaf drop across in the National Forest and across the UK, prompting speculation that autumn has arrived early. But the reality is more complex, and less about the seasons changing, and more about the stress that trees are currently under.
26 Aug 2025
Autumn leaf fall is primarily triggered by day length, which is consistent year after year. No matter how warm, wet, or dry the summer has been, trees “know” when autumn is coming by how much daylight they receive. This means the golden colours of autumn are not arriving earlier this year in the traditional sense.
What we are seeing, however, is trees under stress from the challenging weather conditions of 2025. With below-average rainfall and repeated spells of hot, windy weather, soils in many areas have remained dry for weeks. Wind compounds the problem by drawing moisture from leaf surfaces, forcing trees to work harder to replace the water they lose.
To cope, some species have started to shed leaves early. Leaves turning yellow or brown in late summer are part of the tree’s survival strategy: by reducing leaf area, the tree lowers the amount of water it loses through transpiration. In essence, the tree is regulating its own water use in response to drought.
Silver birch is among the species showing the most visible signs of stress this year. With shallow root systems and a preference for light, free-draining soils, birches are poorly equipped to withstand prolonged dry spells. Many are displaying smaller leaves that have already turned yellow and dropped, reflecting the dryness of the top 50cm of soil where their roots feed.
If August brings wetter weather, there’s still a chance for recovery. A spell of rainfall could encourage stressed trees to produce a fresh flush of leaves, helping them photosynthesise and store sugars before true autumn begins in September and October.
The colours appearing now are not a sign that the seasons have shifted, but a reminder of how sensitive our trees are to changing weather. With rain, many will recover - but this summer highlights just how important it is to build a greener, healthier Forest for the future.
