Why We Use Botanical Nomenclature

Learning the Language of Plant Taxonomy: Explanation of the Binomial System

Image: fall berries of bittersweet vine.
There are three plants that go by the common name "bittersweet." Botanical nomenclature identifies this one as specifically Celastrus orbiculatus. David Beaulieu

For over 200 years we have used the classification model of botanical nomenclature (that is, scientific plant naming) instituted by Linnaeus (1707-1778), the language of plant taxonomy that is employed around the world. Plant taxonomy is the discipline underlying the system of classification used by botanists and horticulturists to organize plants and identify them clearly. Improving on the models developed by his predecessors, Linnaeus simplified the naming procedure through the "binomial" system.

Linnaeus' binomial system uses one Latin name to indicate the genus, and another to indicate the specific epithet. Together, the genus and epithet comprise the "species." By definition, "binomial" means "characterized by having two names," from the prefix "bi-" (indicating "two") and the Latin word for "name," nomen.

For example, botanical nomenclature classifies Oriental bittersweet as Celastrus orbiculatus. The first part of the name, Celastrus, is the genus, the second, orbiculatus, the specific epithet. Although another plant, bittersweet nightshade, also has "bittersweet" in its common name, you know immediately when you see its Latin name (Solanum dulcamara, where the first Latin name is for the genus, nightshade, and the second is for the specific epithet, bittersweet) that it is not related to Celastrus orbiculatus (Solanum and Celastrus are two entirely different genera). A third plant, namely, Celastrus scandens, is also commonly referred to as "bittersweet" (American bittersweet), but the scandens in its botanical name clearly distinguishes it from its Oriental cousin.

Nuts and Bolts of Botanical Nomenclature

  1. The species is a subset of the genus.
  2. The genus begins with a capital letter, whereas the first letter in the specific epithet is lower-case. Both are italicized.
  3. In instances where we translate from Latin to arrive at the common name, we reverse the order of the names, putting the epithet before the genus. This is true in the case of Solanum dulcamara (see above), which translates literally as bittersweet (from dulcamara) nightshade (from Solanum). Note, however, that the common name for a plant is not always a literal translation of the Latin name. For example, the common name for Celastrus scandens (see above) is American bittersweet, but the literal translation of the Latin, in this case, has nothing to do with either "American" or "bittersweet."
  1. Sometimes in plant taxonomy, you will see a third name. In such cases, we are simply getting more specific, accounting for variation within a species. Most commonly, this third name indicates a cultivar (cultivated variety); it will appear in single quotation marks and its first letter is capitalized. But, sometimes, this third name indicates a variety (naturally occurring variety). A variety name is preceded by the abbreviation, "var." Unless the variety name is a proper noun, its first letter is not capitalized. But, like the genus name and specific epithet, the variety name is italicized.
  2. Sometimes yet another word is added after the genus name and epithet, which is neither italicized nor set off by quotation marks -- the name of the person who first described the plant. These names are sometimes abbreviated. When the name is abbreviated as "L," it stands for "Linnaeus."
  3. When you see a genus name followed by the letter "x," followed, in turn, by an epithet, this is an indication that the plant is a cross between two different plant species -- a "hybrid plant."

Why do we use botanical nomenclature? Why aren't the common names of plants good enough? We use scientific plant names (or "botanical plant names") to avoid confusion, since they are an international language of sorts.

That does not mean that they, themselves are never confusing; botanists sometimes decide the current plant taxonomy is "wrong" and change the name. But, by and large, the use of the binomial system described above achieves greater clarity than the use of common plant names.

To look up a particular plant on my website by botanical name, please consult my list of scientific names of plants. Do not be afraid to work with botanical nomenclature. It may seem intimidating at first, but you will soon recognize some terms that appear over and over again, establishing patterns: for example, the use of reptans in the name of a creeper.