Easy Tree ID

You are driving along Pennsylvania highways and notice a scattering of small to medium size trees with the leaves turning brown in July or early August. What's going on here?

There is a very good chance that you are seeing the black locust (Robinia pseudoacacia). Our common locust is frequently spotted in abandoned farm areas and in scattered strips bordering highways. The dark leaves are caused by the locust leafminer (Ondotota dorsalis). The damage is generally uglier than it is desctructive.

I will soon have a complete profile on Robinia pseudoacacia in the Tree Profiles feature.

If you are not clear on the difference between simple and compound leaves and alternate versus opposite leaf arrangements, you might want to review my earlier post: Tree Identification: The Basics (Part One).

We are now developing an approach that should serve you well on summer tree identification (I will cover the more complicated winter indentification process in later posts). Here is a summary of that approach:

1. Are the leaves broad and flat or are they linear or needle-like? The linear or needle-like belong to the the conifers, and we will explore that branch in the near future. For now, we are looking at identifying the broad and flat leaves.
2. Are the leaves arranged in an opposite or alternate pattern along the twig?
3. Is the leaf simple or compound?
4. What is the leaf shape?

We are at number four today, and we will be taking a look at some of the different leaf shapes you will encounter. The terms used to describe leaf characteristics can vary; however, I think they are generally easy to follow. For instance, one source describes a particular leaf margin as toothed and another describes the same margin as serrate. Click on this image to see the general differences you will encounter in leaves.

The most important thing to take away from the tree identification process is a habit of observing and classifying, even as you glance at a tree. For instance, with respect to trees with broad and flat leaves: is the leaf arrangement alternate or opposite, are the leaves simple or compound, and what is the shape of the leaf? Although some will take a little more work to nail down the species, you will usually have arrived at the genus level (maple, birch, oak, etc.) by working through step four.