How to identify a tree

September 23, 6:05 PMPittsburgh Gardening Scene ExaminerRose Field

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Photo by Christopher Field at Longwood Gardens

At some point, when most of us were little kids, a teacher assigned us to bring in tree leaves so we could learn to identify them. Usually in the autumn, we'd collect the most colorful specimens and perhaps press them between pages of a huge volume such as the phone book for a couple of days. This tends to be an activity in the lower grades, so no earth shaking scientific lessons were taught, but we got to know the usual suspects: maples, oaks, plane trees, and every kid's favorite, the buckeye.

Look around your area today and see how many trees you can name. If you mainly observe landscaped areas, the trees may or may not be Pennsylvania natives. Even if you search within a park, or a wooded area, introduced species may have found a home there in the wild.

Trees planted in landscaped sites tend to be limited in variety. There are good and bad aspects to this. Wise homeowners select trees for appropriate growth patterns and ultimate size. Hopefully, as folks grow more savvy to the principle of “right plant in the right place” we'll see fewer instances of massive silver maples planted a few feet from the foundation of a house. On the other hand, many worthy species are under utilized in favor of the same old pin oaks and flowering dogwoods.

When you notice a handsome tree and wonder if it will work on your property, how do you go about researching its characteristics and suitability? Obviously, you first need to learn its name. The first step is probably the easiest: does the tree have needles or leaves? Let's stick with trees with leaves and narrow it down further.

The best clues depend on the season. Is it in flower or does it have fruit at the time? If neither are present at the time, check the arrangement of the leaves. Do the leaves grow off the stem individually (simple), or do they grow in groups attached to a single stalk, maybe in a fan or hand shaped arrangement (compound)?

Do the leaves grow off the stem directly across from each other in pairs (opposite) or do they come off the stem alternately on one side and then the other, spaced a little apart (alternate)?

Simple questions like these, delving into bark, twigs, and other characteristics will eventually narrow down the possibilities and bring you to the answer. Naturally, great online resources can help. For even the newest newbie, try the Arbor Day Foundation "What Tree is That?" step-by-step guide. The Arbor Day site is a terrific place for all types of tree information.

The Pennsylvania Department of Conservation and Natural Resources also provides an informative site for tree ID, Common Trees of Pennsylvania, which shows 57 native and 5 introduced trees of the most common species. Accurate line drawings of leaves, twigs, fruit and seeds make ID easier.

One word of warning from personal experience of three decades working in horticulture: don't be one of the gazillion people who walk into a nursery and begin by describing a tree you're looking for by saying, “I saw this tree I'd like, I don't know the name, but it's got green leaves...”