Photo of Bluebell Woods in Sussex Photo of Bluebell Woods in Sussex

What is Flagging in Trees?

Flagging in trees is a pattern caused by wind killing the branches on one side of the tree only.

Wind from the left of the picture (SW) has killed many of the branches on that side of the tree.
From the book, How to Read a Tree. Illustration by Neil Gower.

From the book, How to Read a Tree:

The wind can do a lot of harm to trees without killing them. Trees in exposed locations struggle, but certain branches suffer more than others. The highest branches of the highest trees get the worst deal, and those on the side the prevailing from which wind comes often fail, leaving asymmetrical tree tops with one side doing OK and one bare side.

The surviving branches point away from the wind, which is why this effect is known as ‘flagging’. In the UK the branches (flags) tend to point north-east. It’s definitely worth looking for this when you’re on hills or near the coast.

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