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Thursday, 26 March 2020

Sycamore and sapwood

This young sycamore has grown 'coppice' shoots after being cut down,
despite the decayed stem leaving just a ring of living wood.
Many ancient trees are hollow yet continue to thrive.

Decay is a natural process within a tree and the photo shows how little sapwood is needed to retain viability.

But why doesn't the sapwood also decay and this Sycamore tree is killed?

Most fungal spores cannot develop within sapwood as it is too high in moisture content and no available oxygen.
The tree also creates a chemical barrier zone, defending the expanding sapwood from the internal decay.
As long as the sapwood can grow and expand to keep pace with internal decay,
there is no reason why this Sycamore could not live for many years as a coppiced stool.

As I understand it, fungal spores are present within trees from their time as a seedling,
which means when fruiting bodies appear after branch removal or damage,
they have often developed internally and grown out of the wound and not,
as we usually think, by spore entry via the wound.

1 comment:

  1. We used to paint tree pruning wounds with a sealant called Arbrex, intended to stop the entry of fungal spores. Then the advice changed because it didn't seem to work. Your last sentence might explain why.

    I had a joke played on me by an old timer gardener. He said to me "look you missed some there for Arbrexing". I knew they were the cut ends of the loose branches really, but I played along with him, which gave him something to laugh about for a many a lunch break.