What’s in a Name? Understanding Botanical Nomenclature

We’re introducing the first installment of the Herbarium department, where we’ll explain scientific names of plants and other common botanical terms, such as cultivar vs. variety, to help gardeners better navigate seed catalogs.

Coneflowers and white fence

Purple coneflowers are in the Asteraceae family.

Photo by istock/andipantz

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Confusing as it is, plants generally have many names, both common and scientific (sometimes called Latin names because of the principal language from which they’re derived). They can also share the same name depending on regional and cultural differences. For example, one group of coneflowers is distinguished by the adjective “purple.” But not all purple coneflowers are actually purple coneflowers. Some are black Samson, or pale purple coneflower, or narrow-leaf coneflower, or Tennessee coneflower, or Topeka purple coneflower — and when you investigate this group of closely related plants, you discover that not all of them have purple flowers! In some cases, a single purple coneflower has multiple common names — black Samson and narrow-leaf coneflower are one and the same. What a mess, right? And I could go on.

In part because it’s human to do so, and in part because it was an intellectual exercise, early philosophers and statesmen in Rome took it upon themselves to provide relatively descriptive names for common plants using Latin. This was fortuitous at the time because Latin was a language known across cultures (think Roman Empire here), and so it helped folks with different cultural and linguistic traditions better understand what plants were being discussed no matter the source of the discussion. This discussion likely pertained more to the curious naturalists of the day than herbal practitioners, farmers, and gardeners.

Fast forward through the fall of the Roman Empire and quite a bit of additional history, and we come to the 18th century, which is smack-dab in the middle of the Age of Enlightenment — a time in Europe when science and philosophy radically changed how folks looked at the universe and all things in it. Not the least significant new concept of the time was that things in the universe could be ordered, categorized, and rationally organized. In this swirling milieu of thought, Carl Linnaeus churned and churned with his keen interest in plant sexual reproduction and descriptive botany, ultimately developing an organism classification system that was both revolutionary for the time and able to withstand the test of time. His fundamental scheme is still in play today.

Sometimes called the “Father of Taxonomy,” Linnaeus gave us the fundamentals of our two-part scientific naming scheme for virtually all organisms. And he chose to use Latin (sometimes influenced by Greek) because it was the “universal” language at the time, at least in educated circles. The scientific names of plants contain two parts that help us identify a plant: the genus, which is usually a noun, and the species (or specific epithet), which is generally an adjective that helps describe the noun. So let’s take a look at some of the plant taxonomy for the purple coneflowers mentioned above.

Understanding Botanical Nomenclature

The true purple coneflower might arguably be the plant called Echinacea purpurea. It’s not too hard to imagine the general meaning of the species name — purple — but what about the genus name, Echinacea? Well, without going into the full etymology of the word, it essentially means “prickly” — literally, like a hedgehog. And that descriptor comes from the mature inflorescence (flower head), which in coneflowers is a collection of hundreds of individual flowers born together. It’s prickly and gets pricklier as it matures into a seed head.

So, what about pale purple coneflower? Its binomial, Echinacea pallida, lets us know that it’s in that group of coneflowers with prickly flowers, but its purple petals are pale (pallida). Narrow-leaf coneflower is universally known as Echinacea angustifolia — narrow-leaved. Certainly it helps to have spent some time with plant taxonomy to know where these species names come from offhand, but you get the point. One of my favorite Echinacea species is the yellow coneflower, also known as Echinacea paradoxa. Here we have a prickly coneflower with yellow petals that’s most definitely not a member of the black-eyed Susan grouping, nor the Mexican hat grouping. It’s definitely a purple coneflower, except its petals are yellow — thus it’s a paradox compared with the rest of its group. Now don’t get all excited and tell me that there are orange and white and other colored purple coneflowers too, because you are absolutely correct. And most of these are Echinacea purpurea individuals that have been developed into named cultivars that are vegetatively propagated for sale to the perennial garden industry.

Purple Coneflower’s Classification History

Now, let’s look back at the classification history for Echinacea purpurea. Linnaeus originally grouped the purple coneflowers with the black-eyed Susan group as Rudbeckia purpurea back in the early 1750s. By the early 1790s, taxonomists had moved purple coneflowers out of Rudbeckia and then back again at least once. In the mid 1790s, the taxonomist Conrad Moench gave the group its own genus, where it has been more or less ever since. But let’s not even think about the number of species, which is now fairly stable at nine species with at least four subspecies. (See? Even plant taxonomists change their minds now and then.) So, if you see that your favorite plant has a new name, don’t sweat it. Classification is based on the tools of measure available at the time. When Linnaeus set things up, he was able to look at the plant and study anatomical details with a hand lens and possibly a crude microscope. These days, we can more closely group plants by looking at their chemical makeup in various ways.

Cultivar vs. Variety

Here’s where it can get more confusing, if you let it. Sometimes you’ll see a plant’s binomial listed with a third word (or phrase) enclosed in single quotation marks, like this: Echinacea purpurea ‘Merlot’ or Echinacea purpurea ‘Cotton Candy.’ These are named cultivars that were formed with human help, and the single quotes are how you represent the cultivars in print — many nurseries will simply call them merlot coneflower or cotton candy purple coneflower, or something like that, but you won’t know if the plant is a cultivar of Echinacea purpurea unless they make that clear. If it’s a named, naturally occurring variety — such as a white mutant of Echinacea purpurea — you would see the variety name after the binomial, such as Echinacea purpurea var. alba ‘White Swan.’

Sometimes you’ll also see the binomial represented without the genus name spelled out. For example, in this piece, we really need only spell out Echinacea as part of the binomial the first time we use it. Then we can refer to purple coneflower as E. purpurea. And we italicize the binomial, or underline it from the old typesetting days, to indicate that it’s a different language — usually Latin.

Identifying Taxonomists

You also might find scientific names with some initials or non-italicized names after them — something like Echinacea purpurea L. or more rarely, Echinacea purpurea Linnaeus — designating the taxonomist most recently credited with naming the plant. Moench would indicate that Linnaeus (L.) first named the plant and that Moench modified the name. This information is really relevant for hard-core taxonomists, but it can give you an indication of for whom and then when (with a Google search) a plant was named.

For most gardeners, the genus, species, and cultivar portions of the plant names are the most helpful when seeking information, advice, and even plants or seed. For more up-to-date information on botanical nomenclature and classification, consult the International Code of Nomenclature (ICN) for algae, fungi, and plants.