What’s My Name: Plant Nomenclature

Plant Naming Origins

Let’s go back in time. Before the age of Linnaeus in the 1700s, plants were typically referred to by common names, i.e., the names that most people used for plants. For example, Basil, Dandelion, and Rose are all common names for plants, and are relatively straightforward. Where it gets as complicated as a tangled vine is when there is one name that refers to many plants. Like, what exactly does “clover” refer to? Oxalis species or Trifolium species are good bets, but not sure bets. Fleabane could refer to many species of asters, which are good insect repellants. Plantain could refer to a small broadleaf weed, or to the edible (and may we add, delicious?) banana cousin. Needless to say, there had to be a better way to refer to plants. Turns out, there is.

The Father of Taxonomy

Carolus Linnaeus, the Father of Taxonomy, was born to a poor Swedish peasant family. Linnaeus’ father originally wanted him to join the priesthood (in those days, a way out of poverty), but Linnaeus had no interest in that. A local doctor took Linnaeus under his wing and taught him all about medicinal plants that were readily available in the region. When he was of age, Linnaeus went to university, but had to transfer a few times as the local universities did not teach botany in a formal way. It wasn’t until his plant herbarium specimen collection had caught the attention of Dr. Olaf Celsius — uncle of Anders Celsius who invented the Celsius scale — in Uppsala that he received the funding he needed, and was asked to teach botany at Uppsala University. Later, he became the President of the Swedish Royal Academy of Sciences in Stockholm and published his greatest work, Species Plantarum (1753), which was the first compendium of plants classified according to his own system of classification.

There were other attempts of classification at the time, with plants being classified to shape or range, but this led to too many names, and did not account for the same species being discovered in new places or completely unrelated plants being lopped together, as well as a myriad of other problems. Linnaeus had a penchant for organization, and had a need to organize things to more easily understand them. He devised a naming system, binomial nomenclature, that used two names to describe a particular species-genus and species. The genus was to be broad, and the species specific—usually an adjective, somewhat following the format of <thing> <adjective or modifier>, e.g. Red maple, Acer rubrum, where Acer = maple, and rubrum = red. He based this system on flower morphology, a radical idea at that time. No one was sure the purpose of flowers on plants but it was hypothesized that flowers could be the sexual parts of plants . After some musing, Linnaeus asserted that flower morphology was relatively conserved among related plants, and that they are the sexual structures of the plants. Turns out, he was right.

Of course, Linnaeus’ friendly demeanor had earned him great popularity, and his lectures were often sought after with his humorous style of teaching and warmth of personality. He loved double meanings and used them liberally in the naming of plants and animals. For example, a species of morning glory is named Ipomoea nil. Nil in Latin means ‘nothing’, which may have you believing that Linnaeus thought nothing of the species. But, a twist! Linnaeus knew that nil also meant blue in Arabic and Sinhalese (Sri Lanka), which accurately describes the blue flowers of this plant. Perhaps blue was his favorite color?

Both Latin and Greek were used for plant naming. Latin was the ‘lingua franca’ at the time, and was the scholarly language used in universities. In fact, until 2012, the International Code of Botanical Nomenclature of plants, algae, and fungi (ICBN) mandated that all new species were to be described in Latin. It’s best to use the Latin names if you can. Worried you can’t pronounce or remember them? Well, it may surprise you that you already know a few Latin names, all without the stress of a pop quiz. Philodendron, Pilea, and Monstera, are all plants whose Latin name is the same as their common name. You may even have one in the room in which you are reading this. And there you have it, you didn’t even know all the Latin you already knew!

Post-Linnaeus Plant Naming

After Linnaeus set the foundation, other taxonomists — people who study classification — have improved upon the original classifications. Although Linnaeus’ original classification scheme was useful, it did not take into account complete relatedness among the plants. A notable reclassification happened in the 1960s where Arthur J. Cronquist reclassified flowering plant species, and formed the two groups, dicotyledonous plants (dicots) and monocotyledonous plants (monocots). Cronquist was an influential scientist, and was one of the few in the western world during the Cold War that taught himself Russian, and travelled to the USSR to translate the works of Russian scientists, which were largely unknown to the western world. The Cronquist System of plant classification was widely adopted from 1968 until 1998, when the current Angiosperm Phylogeny Group (APG) system was implemented worldwide.

In the late 1980s, the ability to use DNA sequencing to classify plants was a new technology, and produces a lot of interesting data that conflicted with the accepted Cronquist system. The famous Chase Study rocked the plant phylogeny world, with the use of the rbcL gene. This gene encodes an enzyme called RuBisCo, the enzyme that fixes carbon dioxide, and makes photosynthesis possible for all plants. This gene was used to determine plant relatedness because not only do all plants possess this gene, but it also mutates slowly, giving a clearer picture over a longer period of time of major evolutionary shifts. The resulting data “rudely shattered” the stability of the Cronquist System for a few reasons, one of them being that the genetic evidence did not support dicots as a distinct clade (grouping). Initially, there was reluctance among scientists to accept the results of the Chase Study due to the fact that only one gene was used, but as more genetic data poured in, it became clearer that the Cronquist System needed a big overhaul. The larger collaboration of scientists that used genetic data to determine plant phylogeny became known as the Angiosperm Phylogeny Group, or APG.

The APG

Since its founding, APG has produced a number of standardized plant classification models, beginning with APG I in 1998. It revises the classification scheme every five years or so, to keep up with new incoming data. Modern phylogeny includes both morphological data, as well as genetic data in determining species and species’ relatedness. Advanced statistical calculations are involved in weighing the ‘characters’ of interest in plants being compared, such as seed size or gene length. Since ancient times, herbarium specimens of plants were pressed and preserved. Currently, to declare a new species, a herbarium specimen of a plant must be created and given to a herbarium to keep. A herbarium specimen is a pressed sample of a plant in good condition, with proper labels, and documented information on what makes that species different from other species. In the old days of plant taxonomy, herbarium specimens were compared to one another to determine and compare species. In reclassification with genetics, DNA can be harvested from some herbarium specimens and used in phylogenetic studies.

That’s Not My Name

The proper way to name a plant is to use its scientific name and cultivar, if applicable. Genus names are capitalized, species epithet are not. Both genus and species names are treated in italics, e.g. Vanilla planifolia. If there is a natural variant, “var” is used with the variant type italicized and all lowercase. For example, Vanilla planifolia var. variegata. If there is a cultivar (usually a hybrid), the cultivar is capitalized, non-italicized, and placed in single quotes. For example, Vanilla planifolia ‘Tahitian Creme’. Something to consider next time you see this — or a “var” of it — on a dessert menu.

The letters that come after the plant name are of course, those are the author’s abbreviation of the first scientist to formally name a species. Sort of like an artist's’ signature on a painting. For example, Triticum aestivum L. was named first by Linnaeus. Each scientist has their own abbreviation, and updates to reclassified species will have the most recent author’s abbreviation. Turns out plants cannot fully be owned!