Question
Hi Jim,

I've got a client with a 25 year old sycamore.  The bark
is badly popping off (in about an 18" section)on three of the
main branches.  The wood underneath looks dark brown. There is virtually no tip dieback, and the rest of the tree
really looks healthy.

Looking forward to hearing your opinion of what is going on
with this beautiful tree.  

Answer
This is normal fo sycamore tres. Although it may be disturbing to see bark strewn all over your lawn, if you have a sycamore or a London plain tree, this bark shedding is perfectly normal every year.

What happens is as the trunk and branches increase in diameter every year, these trees, instead of having furrows of bark, like a maple or oak tree, the bark on a sycamore or plain tree is more in a plate form.

As the trunk increases in diameter, it simply cracks and falls to the ground. This reveals multiple colors of bark from the creamy yellows to the tan to the browns, which can really be quite attractive.

It is nothing to worry about. You cannot prevent it and you certainly don't want to try and prevent it. That is the way these trees grow.