How to Identify a Tree by Use of a Key

A key is arranged to aid the user to the right identification of the organism they aren’t sure about. Leaves and flowers sometimes are the easiest way to tell what a tree is during a certain season. Since this doesn’t always work, the key is a helpful way to figure it out.

As an example, suppose we have a specimen of black locust, in summer.  Turning to the Summer Key, Page 12, we have the choice of A1, Leaves Evergreen, or A2 Leaves Not Evergreen.  Since it is evident that the leaves of this tree fall each autumn (not evergreen), we are directed to F.  The description of F1 does not fit so, we look at F2 “Leaves larger, broad, flat; fruit not a woody cone, “which fits and we proceed to G.  The first G fits, for the specimen usually has a pair of short spines at the base of each leaf.  Next, we find that H2 fits better than h1.  At J, we find the trail of “At least some spines in pairs at the base of compound leaves” and go on to K.  K fits exactly and we have the identity as black locust (Robinia), and turn to the page indicated.

However, there are times when this same tree may not have any evident spines.  In that case then, the search would go on to G2, instead of G1, and then to P, “Leaves compound (blade in more than one part)” fits our sample and leads to Q.  As Q1 does not fit, we proceed to Q2 “Leaves pinnately compound, and on to R.  R2 fits better that R1 and so does T2.  At V, the chose is in the kind of fruit.  This may not be too evident at certain times of the year,  but some of these can usually be found on or under such trees except in the case of young trees.  V2, “Fruit a small flat pod,” leads us to the name black locust (Robinia).

Thus the identification of this specimen in summer would follow the path of these in the Summer Key:  -A2, F2, G1, H2, J1, k1.  In the winter key:  A2, B2, C19 D21 F119 f1.

Dogwood:  A2, F2, G2, P2, X2, Y2, Z2, AA.

Now that you have a good idea of what to do, try it on a leaf or tree you already know.  After doing this, try some unknown species.  It should be easy to use this key while identifying leaves you need to know in a short period of time.

- Written by Kelsea Sneed, Ryan Anderson, and Chelsey Howard