When you head into the woods across most of Pennsylvania and find a tree with opposite leaves, it is most likely a maple or an ash. If the leaves are simple, it would be a maple and, if compound, an ash. There are exceptions to this rule, and in future posts I will cover those exceptions (buckeyes and catalpas).

I offer the comparison of ash and maple tree leaves as a demonstration of how easy it can be to start mastering tree identification. It is only a first step, but I think you will be pleasantly surprised with your increased level of awareness with respect to trees if you start with that tidbit.

So we do we mean when we use the terms opposite, alternate, simple, and compound with respect to leaves and tree identification? I have provided a diagram (click to enlarge) that will give you a good feel for what those terms mean when applied to trees. You may find it difficult to tell the difference between leaflets on a compound leaf and a simple leaf. Here is the secret: Leaves have buds at the base, but leaflets do not. Work your way back until you find a bud, and you would be able to know whether you are looking at a simple or compound leaf.

The bottom of the diagram includes the three primary types of leaves found on evergreen trees: needle-like, scale-like, and awl-like. I will cover those in the near future when we start looking at identifying evergreens.

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