17/09/2026
🍂 WHY DO LEAVES FALL — AND WHY DO SOME REFUSE TO LET GO?
As we get nearer the Equinox, something remarkable is happening in our deciduous trees — right at the point where each leaf joins its twig.
As daylight shortens and temperatures fall, these trees begin preparing for winter. Chlorophyll (the green pigment) is broken down, revealing the yellows and oranges that were there all along. Useful nutrients contained within the leaves are recovered and stored in the more permanent parts of the tree, ready to be used again.
🍂 Then comes abscission.
At the base of each leaf stalk, an abscission layer develops — a specialised layer of cells that gradually weakens the connection between leaf and branch. Eventually gravity, wind and weather help finish the job.
You may notice the little leaf scars left behind — and these can remain visible on the twig for years. Horse chestnut has a particularly lovely one, often described as looking like a tiny horseshoe!
🍂 Why drop the leaves at all?
Perhaps, a little like us humans, it’s time to slow down and conserve resources through the winter months. Leaves are costly to maintain and vulnerable to frost and winter weather.
There’s another benefit too. The ground beneath the canopy becomes littered with fibre-rich gifts. Fungi, bacteria and other decomposers gradually break this material down, returning nutrients to the soil to be recycled through the woodland ecosystem.
🍂 The exception that proves the rule?
Not every tree lets its leaves go straight away.
Look at young beech or oak trees in winter and you may well see papery brown leaves still clinging to their branches.
🍂 This is called marcescence.
🍂 Why — I hear you ask?
There are several theories. Retaining leaves may help protect young buds from hungry browsing animals, and delaying leaf fall may affect when nutrients are released into the soil beneath the tree. Scientists are still exploring exactly why some species — and particularly younger trees and lower branches — do this.
🍂 Something to notice this autumn…
LochLeven
