The Naming of Plants
- susan5383
- Apr 19
- 10 min read
By Patsy Cotterill
The Binomial System
Being able to name a plant or animal is the first step in getting to know it. One can observe and become familiar with an organism without knowing its identity, but knowing a name, especially if it is a scientific name, allows you not only to communicate about that organism but also gives you access to all the information, beyond your personal information, that has been accumulated about that organism.
All living things that are known to science have at least two names, a genus name and a species name, both in Latin and both italicized. The genus name always starts with a capital letter and the species name with a lowercase letter. This is the binomial system of nomenclature (although in the case of zoological nomenclature it may be referred to as the binominal system). It applies to all organisms: animals, plants, fungi, algae and bacteria. For example:
Tyrannosaurus rex
Homo sapiens
Rosa acicularis
Pleurotus ostreatus (oyster mushroom)
Chlamydomonas nivalis
Escherichia coli
Going back a few centuries, when the educated elite were prone to communicate in Latin and Greek and the Classics were as popular a choice for university students as computer science is today, it was natural to describe plants with a string of Latin words. The genius of the great Swedish botanist Carolus Linnaeus was to cut this string down to only two words, which thus became an identifying label or name for the organism. He formalized this binomial system in his publication Species Plantarum of 1753. The two-word name becomes a short and unique identifier, and coded in the dead (and therefore unmodifiable) Latin language, it is recognizable throughout the world.
The International Codes of Nomenclature
As you may imagine, for any system to be valid and applicable world-wide it must follow strict rules, which makes the assignment of a binomial serious business indeed. These rules are set out in the International Code of Nomenclature for algae, fungi and plants (ICNafp, formerly the International Code of Botanical Nomenclature) and the International Code of Zoological Nomenclature (ICZN) for animals. The codes are kept up to date at regular international congresses.
Naming Distinct Populations within Species
The two International Codes differ slightly in their application; for example, when a third name (trinomial) is added to indicate a rank below species level. Within a plant species, a distinct set of populations may be recognized as a subspecies or variety and this infraspecific rank is indicated with the word subspecies or variety (usually abbreviated to subsp. or var., and always in Roman font) in front of the third name: e.g., Helianthus pauciflorus subsp. subrhomboideus (rhombic-leaved sunflower) or Erigeron glabellus var. pubescens (hairy streamside fleabane). However, in the case of animals the trinomial can be placed directly after the binomial, e.g, Bison bison bison (plains bison) and Bison bison athabascae (wood bison).
Incidentally, this reveals another difference between the codes: animals can have the same genus and species names, whereas plants cannot; the specific name must always differ from the generic. Because the two codes operate independently, in a few rare cases an animal and plant can have an identical name!
It should be noted that the recognition of a subspecies or variety also changes the common name of a plant or animal. Thus, recognized only at the species level, Maianthemum canadense is just wild lily-of-the valley, but if we are referring to Maianthemum canadense subsp. interius, the variety we have in Alberta, it is called western wild lily-of-the-valley. In practice, and in common parlance, we are pretty careless about applying common names, and generally we have not been in the habit of recognizing infraspecific ranks. Genera also have common names and sometimes we shortcut, calling a species by the common name of a genus. A typical example is the common dandelion, Taraxacum officinale, which we refer to as just dandelion, although this is strictly the common name for the whole genus Taraxacum, encompassing a number of dandelion species.
Recognizing and Naming a Species
How does a species come to be recognized as a distinct type of organism and given a name? In the case of plants, it is described in detail and given a binomial by a person who then becomes its author (or authority) and whose name appears after the Latin binomial. (Until recently, the description had to be in Latin, but this is no longer the requirement.) The description is published in the taxonomic literature and it must refer to a physical specimen known as a type specimen, which is usually housed in a herbarium (a library of dried plant specimens). Fellow taxonomists will then decide whether this is a valid species or not, and whether the name is valid according to the rules of nomenclature.
Random examples are: Lotus corniculatus Linnaeus (usually abbreviated to L.) and Chrysosplenium iowense Rydberg (abbreviated to Rydb.), established by botanists Linnaeus and Rydberg, respectively. The author(s)’ name(s) is/are included in formal written works and scientific articles, but usually omitted in popular guide books, apps and casual writing.
Latin Names Can Change
Because Latin names are unique, whereas common names can be many and vary locally, serious botanists are always advised to learn the scientific (Latin) name. However, this does not mean that Latin names do not change, as most of us know from experience. There can be several reasons for this, and the change is not always universally accepted among taxonomists. Most changes are the result of further research and knowledge of the species concerned.
One problem is that, in the days before communication was fast and easy, the same species could be described by more than one person, resulting in synonyms - different names for the same entity. In this case it has been the job of taxonomists to figure out the valid or accepted name by determining which one was the first to be published validly or, in other words, which name has priority.
Sometimes a very common plant has been named many times with a ton of synonyms, and sometimes the species name can even change back and forth. For example, you will find our harebell or bluebell of Scotland is Campanula rotundifolia L. in Flora of Alberta, which is also the current name in Canadensys Vascan, the online database of Canadian vascular plants. However, in the meantime, it has also been called Campanula alaskana (A. Gray) W. Wright ex J.P. Anderson, as well as a few other names. Note the change in authors with the alaskana synonym. American botanist Asa Gray once called our North American plant Campanula rotundifolia L. var alaskana but then I presume W. Wright, following J.P. Anderson, decided that the variety was distinct enough to be elevated to species level, i.e., Campanula alaskana, recognizing that Gray had first coined alaskana as a varietal name. I can only assume that further taxonomic research has revealed that the North American species is identical to the European one originally named by Linneaus, and so we return to C. rotundifolia L. When such name changes occur with new and/or additional authors’ names they are called new combinations and their history can get very complicated – rabbit holes I don’t advise anyone but the nerdiest taxonomist to go down!
In other cases, further research may indicate that we are not dealing with a synonym but that a species may be a quite different taxon from another species with the same name, in which case one of the species has the “right name” and the other is renamed.
Yet again, molecular and DNA analysis may show that a plant’s genetic relationships do not accord entirely with its morphology, and it needs to be moved into a whole new genus or even family. Seaside buttercup (or seaside crowfoot) has happily been a buttercup, Ranunculus cymbalaria Pursh, until recently, but is now separated out from its Ranunculus cousins as a lonely Halerpestes cymbalaria (Pursh) Greene!
Keeping Current
Unless we have access to elite taxonomic literature, ours is not to reason why, but simply to keep up with the new names if we wish to communicate accurately!
Normally I submit to name changes with a good grace, professing only mild annoyance at the inconvenience of having to change species lists, records, etc. In some cases, however, I feel extra allegiance to the old names. Sandgrass, Calamovilfa longifolia Hooker, used to refer to a beautiful tall grass that is abundant locally on sand dunes and in well-drained grasslands. It has undergone a spectacular migration to the genus Sporobolus, and acquired the full name of Sporobolus rigidus (Buckley) P. M. Peterson var. rigidus, acquiring the common name of prairie sandreed. This is personally disturbing, because the other Sporobolus species I am familiar with, Sporobolus cryptandrus (sand dropseed), bears little resemblance! The genus Sporobolus also now includes two other species, the cordgrasses (formerly Spartina species), that again look very different from both prairie sandreed and sand dropseed. The common name change is of interest here because it appears that it has retained reference to Calamovilfa rather than Sporobolus. The latter means dropseed, but the calamos in Calamovilfa is Greek for reed! Then there is the matter of the gender change from attractive feminine Calamovilfa to the ugly masculine Sporobolus! I can imagine that when Linda Kershaw and Lorna Allen were compiling their Vascular Flora of Alberta: An Illustrated Guide and carefully checking Canadensys Vascan for the latest names, they got some eyebrow-raising surprises!
Canadensys Vascan
Speaking of Canadensys Vascan, this is the go-to database for information on the status of vascular plants in Canada and Greenland. I check it constantly for the correct spelling of Latin names and common names.
There is a page for each species, and subspecies or variety where they exist, accessed by clicking on Name Search on the website and entering in the name (preferably the scientific one, but the common name can also work). The example I have chosen to illustrate in Canadensys Vascan is Maianthemum canadense, wild lily-of-the-valley, and its two subspecies, subsp. canadense and subsp. interius.
Above is the upper portion of the species page for Maianthemum canadense indicating its full name and its author (Desfontaines), as well as the authority by which that name has been accepted as the one for preferred use.
This is followed, if appropriate, by a list of vernacular (common) names and their authors, although in this case for the species as a whole no synonyms are listed. The map shows the distribution of the species in Canada; the green colour indicates that it is native in those regions, grey denoting where it is absent.
The lower portion of the page shows the species’ position in the classification hierarchy of subfamily, family, order and higher groups. It also shows that two subspecies are recognized: subsp. canadense, also known as the typical subspecies (or the plant corresponding to the type specimen on which the species is based), and a second subspecies, interius.
To access the page on subsp. canadense, click on the link on the species page. Note that the subspecific name is the same as the species, i.e., canadense, but the common name has changed to eastern wild lily-of-the-valley. Synonyms are now listed.
The lower half of the page shows the more eastern distribution of the typical subspecies suggesting that the species was first recognized by botanists in eastern North America.
Returning to the species page and then clicking on subsp. interius we find the following:
The Latin name has become longer and now has extra authors tacked on, to indicate the authors of the subspecies: (Fernald) A. Löve & D. Löve. From the synonyms list we see that Fernald first recognized the taxon as a variety, which is how it will appear in the older literature, but the Löves upgraded it to the somewhat higher rank of subspecies, possibly because of its overlapping but different geographic distribution from subsp. canadense, as shown in the lower part of the page.
Looking at the various ranks in the taxonomic hierarchy above the genus level shows that they are also subject to naming protocols. Thus, for example, families always end in "aceae" and orders always in "ales" (neither are italicized). As practical botanists, we are mostly concerned with genus and species, although familiarity with the family a plant belongs to can be very useful, especially if one is using a key for identification. Orders determine the arrangement of families in a guide book (which is not alphabetical) and reflect evolutionary relationships, with progression being from the more primitive to the more evolved families.
What else can we learn from Vascan about changes in taxonomy and hence names? In some instances, previously recognized subspecies and varieties are discounted as invalid and subsumed within the species, making identification easier; in other cases, new infraspecific ranks have been recognized, resulting in recombinations with more authors involved, and usually a longer common name. We saw that was the case with wild lily-of-the-valley, which became western wild lily-of-the valley to distinguish subsp. interius from the eastern wild lily-of-the-valley, subsp. canadense. Often with these new combinations, Vascan creates a common name that is a close translation of the Latin name. Kershaw and Allen now recognize subspecies and varieties in their Vascular Flora of Alberta. An Illustrated Guide, which can add further precision to our identifications and necessitates checking Vascan for the accepted infraspecific names. (More on this in Part Two, when we take a quick look at using a key.)
In a second part of this article, I will explore some of the meanings of the Latin and Greek names applied to plants. Some words will already be familiar because they exist also in the general language.
References
Canadensys Vascan https://data.canadensys.net/vascan/search
Kershaw, Linda J. 2019. Alberta Plant Names. A Guide to their Pronunciation, Meaning, and English Alternatives. Self-published. Note: The Latin and Greek derivations of the plant names used in the illustrations here are taken from this book.
Kershaw, Linda and Lorna Allen 2025. Vascular Flora of Alberta. An Illustrated Guide. Second edition. Self-published. Kindle Direct Publishing.
Moss, Ezra H. 1982. Flora of Alberta. Second edition, edited by J.G. Packer. University of Toronto Press, Toronto.
