Peeling Trees

Growing up in Edmonton, Alberta, Canada I only knew of one tree where the bark would peel off: the birch tree. While this peeling is very historically significant as local First Nation groups would take advantage of the ability of the tree to peel and survive to make birch bark canoes for a white girl in an urban centre it wasn’t much more than a novelty. Part of this I think is that it isn’t very spectacular. Small patches of the tree look yellow where the bark has peeled but it is small patches and the tree basically looks the same, just a slightly different colour. Now, biologically it isn’t quite the same because this inner layer is actually the cambrium

The first time I remember seeing a tree where peeling seemed like something special was an Arbutus tree on Vancouver Island. When these trees peel you notice. They peel in big sections: red papery bark curling away from the tree in large sections, revealing greenish tan bark layer below. I think they stand out more because it happens in larger sections at a time and the colour change is so significant compared to my local birch trees.

On a recent trip to California to attend Sci Comm Camp (sadly on its last year), I was struck by a peeling tree I didn’t know. Thankfully one of the other campers (@a_student_of_nature on Instagram) graciously id’d the tree as eucalyptus for me. Here are a couple photos I took of the trees.

What a distinct change! The peeling bark looks rough, while the tree underneath looks young and smooth. This I think makes it easier to understand what the tree is doing when it sheds its bark.

So basically most of the trees that peel have pretty smooth bark. But as the tree gets bigger the bark can’t expand. On trees with rough bark, the bark will crack and them new bark will form to fill in the crack. But with smooth bark trees these cracks would mess with the smoothness, so the tree responds by shedding the outer layer and forming new bark. This is pretty similar to insects needing to shed their exoskeleton (the hard outer covering) in order to grow. Or, in more familiar terms, when we no longer fit our clothes for some reason and have to get bigger clothes.

So, I learned how to id a new tree and it helped me understand why some trees shed their bark.