Why does my sycamore have brown leaves?

Question

I'm in the UK (Gloucestershire) and have a mature sycamore (Acer pseudoplatanus) at the edge of my garden, which was planted by my neighbours between 40 and 60 years ago (the survivor doesn't remember when her husband planted it on the boundary of the field outside their garden 'on a whim').

16 years ago, when I moved into a house newly built on the field next door, I had the sycamore pollarded (it was far too big to contemplate otherwise). Since then, it has been pruned by professional arboriculturists every 2-3 years in winter to keep the height under control i.e. to less than the height of a two storey house. This allows my neighbours to use the greenhouses they sited under the tree they planted, but allows me to have useful shade at the side of my back garden -- and I've planted the borders to allow for this.

Recently however (last 4-5 years), I've observed a section (always the same section every year) of the leaves browning at the edges and eventually falling prematurely. The rest of the tree seems healthy, but the effect is unsightly and gives me concerns about the overall health of the tree.

What could be causing this, and is it capable of remedy, or do I need to sacrifice the important shade and replant my borders?

Answer 1

If that has happened every year for five years or so, and always the same branch, then some serious inspection of the woody parts and the main trunk of the tree is called for. There may be some type of rot or other problem in a specific area that causes it, and if its just in that one branch, it would be better to have that particular branch entirely removed.

Sycamores often suffer serious bark damage from squirrels - they strip the bark off and if that stripped area is all around a branch, then the branch gets die back. There is also a fungus that affects these trees in damp parts of the country (Cristulariella depraedans) - this causes leaves to fade and die, but any so affected leaves will show what looks like white splashes on the leaves. Neither of these problems really explain away the fact that its always the same part of the tree that is affected during the last few years.

If you are not able to inspect the branch and trunk properly yourself, then next time you have your arboriculturalists out to prune the tree, get them to check it over properly. It might be helpful if you can mark the branch concerned in some way (spray paint maybe?) so they are able to focus their attention where the problem is, but they should also inspect the entire trunk and woody parts at the same time.