This time of year, with no leaves on most trees, I depend mostly on the twigs, buds, and bark of the tree. Some trees are easily identified from afar by their bark, such as shagbark hickory (Carya ovata). For other, more difficult to identify species, I begin by looking at the twigs. The most important characteristic of the twigs to note is how the buds or secondary branches are arranged on them. Most of the trees in my region have the buds emerging alternately on the twig. That is, one bud will emerge on the left side of the twig, then the next will emerge on the right side, continuing along the twig. This arrangement is usually modified by the opposite pattern on emergence spiraling up the twig, so that looking at the twig on end, the bud placement resembles a spiral staircase. Oaks, elms and cherries are common examples of this arrangement.
Less common is the opposite branching habit, where two buds will emerge opposite each other on the twig. Again, this pattern is usually modified such that each successive pair of buds emerge perpendicular to the previous pair. This arrangement is common on viburnums, maples, dogwoods, and ash trees. Opposite branching habit is a particularly useful characteristic to note because relatively few trees bear their branches oppositely.
Opposite Branching Habit
A third branching habit is the whorl. A whorl is where three or more buds emerge together on the twig. Trees bearing the whorled habit are even fewer that opposite branched trees. Catalpa is a common example. Pines, spruces, and firs are also examples of trees with a whorled habit.
Once you have identified the branching habit of the tree, the next step is to examine the buds. I will talk more about the buds and other characteristics in following posts.