Branch sinuosity in old trees

[Bosque]

Why do the branches of some species of old trees twist?

Thanks,
Carol Diamond

[RayA]

Hi Carol,

The "gnarly", sinuous look of old tree limbs can be caused by repeated breakage due to storms, wind, ice/snow loads, etc, over long periods of time (often centuries). When the end of a branch is broken off, a side bud grows out to become the new branch tip leading growth point; because it's a side bud, the branch growth takes a slight change of direction, at least for a while. Repeated damage eventually creates the gnarly look. Also, when a neighboring tree goes down or is damaged, more light may now reach the limb, causing its growth to orient toward the increased light (again causing sinuosity). Over great lengths of time, ancient trees can often end up with a relatively few thick, twisted limbs, giving the trees that look of antiquity that speaks of time and survival.

In this photo of a grand old black birch, you can see where limbs took a change of direction at the points where branches had broken off and side buds took over.

Old Black Birch

[Bosque]

Thanks, Ray, for taking the time to explain this phenomenon.

Carol