skin, blood and tears
Walking along a busy suburban street, I admire the beautiful complicated patterns of the bark on the street trees. This is nature that can be appreciated as abstract art. Trees also evoke a sense of spiritual wonder, especially old trees. The bark is the skin of the tree, and very important, like human skin, for protecting what is inside.
These are photos of London Plane Trees, Plantanus x acerifolia. The bark has that pattern because it breaks away in large flakes to enable the tree to cleanse itself of pollutants. This must why it copes so well in urban spaces, and is such a popular choice for street planting.
A tree is also a habitat, and in the photo above we see a colony of moss growing on its hospitable trunk
If bark is the protective skin of the tree, then sap is its blood and tears. The following photos, of a Ghost Gum, Corymbia aparrerinia, were taken by Marg, a friend of mine.
Like bark, sap serves as a protective function for the tree. Sap flows through the outer part of the trunk called sapwood. Sapwood consists of actively growing cells and carries water, minerals, hormones and nutrients from the roots to the branches. Sap normally belongs inside the tree. When it oozes out, it is a sign that the tree is suffering from disease, pests or pruning. It's weeping or bleeding.
My dog Potter is also fascinated by trees. Here she is wondering why on earth humans call it bark.