A Tree-Spotter's Guide to Bark: Part 1

When you think about it, the bark of a tree is pretty remarkable. It's the tree's self-healing protective layer, defending the thin layer of living phloem cells inside, just below the surface, that conduct sugars up and down the stem and also protecting the living layer of cambial cells that produces new growth every year. It's waterproof, but it lets gases pass in and out and it's capable of expanding to keep pace with the growth of the tree, splitting and cracking as the tree ages in a pattern that's characteristic of each tree species. On one January day twenty-seven years ago the bark of this beech Fagus sylvatica was the canvas on which SP and CS carved a declaration of their undying affection; thankfully the wound healing properties of the bark meant that the tree still thrives, even though the union of SP and CS may or may not have endured.

The bark is a tree species' fingerprint. This is Scots pine Pinus sylvestris, with its irregular plates of warm red-brown bark that perfectly complement the deep, glossy green of its needles - especially when winter sunlight strikes the trunk.

The barks of pedunculate oak Quercus robur and of Durmast oak Q. petraea can't really be distinguished, so this could be either (although I happen to know that it was the latter because the acorns had no stalks). I think it may generally be the case that slow-growing trees like oak develop a rugged bark of ridges and fissures that are slowly added to with age, while fast growing species like sycamore and birch tend to develop more rugged splits or shed bark more readily. 

Sycamore Acer pseudoplatanus bark is smooth when the tree is young but soon develops into flattened, irregular plates that are slowly shed as the tree ages, flaking away to reveal a fresh layer below.

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