Naked Trees

Often when walking through the woods in winter, it's hard to identify the trees since they don't have their leaves.  I think of it as looking at people with no skin and hair.  Could you identify me by just my bones?

But there are clues and I'm trying to learn them.  Twigs are the easiest.  The arrangement of the twigs on branches is one sign.  The pith (the core of the twig) and leaf scars set species apart.  Finally, the bark identifies the tree.  But you have to know the differences between a young, middle-aged or old tree.