Many tree care folks have heard, and perhaps even said, the classic, “Well, I don’t know what it is, but I’ll trim/cut/prune/take it down for you.” Though hearing or saying it might bring a wry smile to the face of many tree care professionals, it should also bring, at the least, a slight twinge of embarrassment. After all, how comfortable would you be hearing a similar phrase from another professional, such as a mechanic, doctor or lawyer? This is not to say that a tree care professional must know every species of tree in existence. An arborist cannot be expected to immediately identify every individual species within the wide variety of cultivars, exotics and ornamentals existing in the landscape. Yet, a basic knowledge of tree identification should be an inherent part of being considered a tree care professional; not only to choose appropriate treatment or care, but also for the safety and well-being of the climbing arborist themselves. A safe tie-in or rigging point in an oak is likely to look much different than one in a cottonwood to a tree crew member who can distinguish between the species, while looking very much the same to one not versed in tree identification. There are many excellent tools and resources for learning and assisting tree identification, but a few basic principles and concepts are an excellent place to begin the process.
The form of a tree, in the context of tree identification, refers to a species’ typical shape or outline. Though, in most cases, it should not be considered a definitive indicator of a tree’s species, as there is certainly more than a little variety amongst all individuals of the same species, but it can certainly start the identification process in a general direction, particularly when viewed from a distance.
The knowledge of different species’ typical bark texture, color and other general characteristics can be quite valuable in tree identification, and is useful with larger trees when a visual examination of leaves or buds is challenging. In some cases, trees are readily identifiable simply from their distinctive bark, but caution should be employed as there are species where the bark can vary with age or environmental conditions.
This refers to the pattern in which the leaves are attached or arranged on the stem or twigs, and can often give an excellent clue as to what tree species the identifying party should be considering. Leaf arrangement is typically referred to as one of three types: whorled, opposite or alternate. A whorled leaf arrangement will have multiple leaves around the stem at the same spot, while an opposite one will have two leaves on either side of the stem at the same location. In an alternate arrangement, the leaves will be staggered or alternating on either side of the stem.
Tree identification in winter, or when leaves are simply not present, can be quite challenging, and knowledge of the form, shape and structure of different species’ buds can be quite helpful in this regard. Obviously, the bud arrangement is going to fall into the same categories as the leaf arrangement discussed previously, but particular bud characteristics, such as scale location or bud shape, are useful and can identify individual species once known and understood.
The pith, or interior wood structure, of a twig from a particular tree can also offer information of value to the identifying arborist. Although in many cases the twigs may not be readily available, or their pith all that distinctive, trees, such as a walnut and its pith, which has multiple small cells or chambers, are quite easily identified in this manner.
The most common method of tree identification is obviously through examination of its leaves or needles for distinctive characteristics, and though obvious, this method requires more than a small amount of knowledge of different terms and characteristics. Among these characteristics are ones such as whether a leaf is simple or compound; if compound, is it pinnate or palmate, if simple, is its margin entire or lobed, and many more. A simple leaf is just that, simply one leaf springing from a bud, while a compound leaf has multiple leaflets springing from its petiole, which arises from a bud on the stem. A compound leaf that is pinnate has leaflets attached along its petiole, much like a feather, thus the name, while a palmate leaf can look like the fingers off the palm of a hand with leaflets attached at the end of the petiole. A simple leaf with an entire margin is one in which the edge of the leaf is smooth with no serration, while a lobed leaf has distinctive and severe indentations in its margin. Needles may appear singularly or in bunches of various numbers; and may also be scale or awl-like. All of these multiple characteristics provide the tree care professional with information that, once understood and deciphered, can provide the tree’s identification quite readily.
A tree’s fruit and flowers, like the leaves to a certain extent, are often only available at certain times of year, but, when present, can provide ready identification of an individual’s species. In the case of conifers, cones often linger on the ground or, in some cases, on the tree for an extended period of time, and in larger trees can provide evidence of what species the tree is even when the needles are far beyond view, though care must be taken not to be misled by adjoining trees’ cones.
The trials and tribulations of learning the scientific, botanical or Latin names of trees has been the bane of more than a few tree care professionals’ existence, and many simply refuse to learn or use them. Although learning the scientific names of trees can be, and often is, a challenge, it is important to at least attempt it for a number of reasons. Common names can not only be confusing in discussions with fellow professionals or customers, they can also be misleading and sometimes result in incorrect treatments or work practices. There are many trees of extremely different species and even genus that have the same common name leading to confusion; and other species whose common name misleads the user as to its true identity, such as firs that are not firs. Additionally, though no one needs be fluent in the ancient language of Latin to take advantage of this feature, the scientific names of trees can, and often do, describe a characteristic of the tree. An example of this would be the big leaf maple whose scientific name is Acer macrophyllum. In this case, the genus of the tree is Acer, as are all maples, while macrophyllum means big leaf; and the big leaf maple is known for its large leaves.
As can be drawn from the small amount of information conveyed here, tree identification can be a subject of vast breadth and complexity, one that can quickly become overwhelming. A simple, straightforward guidebook and attention to the numerous tree features/characteristics that tree professionals see “up close and personal” on a daily basis will go a long way toward better identifying individual trees. This will in turn help them care for the trees more appropriately in a safer manner; and help them avoid ever having to say “Don’t know what it is, but I’ll take it down for you.”
Michael (House) Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions/Arbor Canada Training and Education, currently located in Lancaster, Ky.