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Georgia Gardener Newsletter Design: January 10, 2008

Nomenclature: The Science of Plant Names

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Introduction

Scientific (aka Latin or botanical) names has been used for centuries to properly identify the thousands upon thousands of different plants found all over the world. The use of scientific names has also been used for the same purposes in animals and all other living creatures. Without the use of standardized scientific names, we would never be able to sort through all the creatures that inhabit this planet.

Many gardeners shy away from the use of scientific names and opt for the more convenient (yet more confusing) choice of common names. While common names are great to start with, many plants have multiple common names and some distinctly different plants share the same common name. What a mess. By using the scientific name, each plant has one and only one standardly accepted name, although they may periodically change. When searching for a specific plant using the scientific name is the only way to ensure that you have the correct plant.

I'll admit that learning and keeping up with the scientific names can be challenging, especially since the science of plant names is not static. Plants are constantly being reclassified and named by professional botanists through the International Botanical Congress who maintain the International Code of Botanical Nomenclature. Even I get a headache when trying to sort it out. So, I will simply try to cover some of the basics that can be extremely helpful to gardeners.

Basic Definitions

Before we get started with a basic discussion of scientific names, let's define some commonly seen terms:

Taxonomy: This is the study of the principles of scientific classification. If you remember back to your basic biology, this is where you studied things like: Kingdom, Division (was Phyllum), Class, Order, Family, Genus and Species.

Nomenclature: The internationally accepted standardized use of Latin names for plants (and animals).

Binomial Nomenclature: The use of two Latin names for naming each living plant (or animal). It is comprised by combining the Genus and specific epithet.

There are other terms that apply more specifically to plants such as cultivars, varieties and hybrids which we'll cover below. If I have bored or overwhelmed you, stick with it. I'll use some common examples below.

A Common Example

Let's use a plant known to all gardeners which may help you to understand the use of scientific names as applied to plants. For our purposes, we will use the red maple.

If you research the red maple, you will undoubtedly run across the following:

Acer rubrum L.

The term "Acer" is the name of the genus to which all maples belong. The term "rubrum" is the specific epithet and simply means red. (Note: All botanical names follow a standard format in that the genus is capitalized, the specific epithet is not and both are italicized.). The non-italicized capital "L." after the scientific name is the abbreviated letter code of the botanist who has been internationally recognized for naming the plant. In this case, the L. stands for Carl Linnaeus (1707-1778) who is considered to be the father of plant taxonomy.

But all good gardeners know that there is more than one type of red maple. In fact, there are more than a dozen. So, you may see something like this:

Acer rubrum 'October Glory'

Often by this time, the botanist's credit has dropped away. The name that follows the scientific name (contained in single quotes and non-italicized) is known as the "cultivar." The cultivar (a combo name derived from cultivated variety) is defined as a cultivated plant that has been selected for its unique characteristics and which is genetically identical to all others of the same cultivar.

Since cultivars are all reproduced asexually either from cuttings or tissue culture, they are clones and thus can be expected to have similar/identical growth habits, when grown in similar environments.

Another Example

Let's use the sugar maple for our next example which will also bring to light some controversy and disagreement amongst botanists on the classification of some plants.

Acer saccharum ssp. leucoderme

Once again, "Acer" is the genus for all maples and "saccharum" means sugar, but now we have a non-italicized "ssp." followed by an italicized "leucoderme." In this case, the "ssp." is an abbreviation for subspecies. This tree is considered to be a sugar maple but a population of some have genetic differences significant enough to have them further subdivided. However, not all botanists agree that this tree (commonly called the chalk maple) is a subspecies and so they refer to it as a separate species: Acer leucoderme.

Other Commonly Seen Name Configurations

There are other peculiarities seen in botanical nomenclature. These include:

X - This refers to plant hybrids such as: Amelanchier x grandiflora. This serviceberry tree is a naturally occurring hybrid of A. arborea and A. laevis (note the accepted abbreviation of the genus when the subsequent plants mentioned are in the same genus as the one immediately preceding).

Var. - This refers to plant varieties. Varieties are naturally occurring variations that resemble the species but may have mild differences in one or a few characteristics from the mainstream (straight) species. They have the ability to interbreed with other varieties and the straight species which often results in the loss or blending of their differing characteristics. An example would be the naturally occuring dwarf juniper: Juniperus communis var. depressa. The variety is also italicized.

® and TM - These are registered and trademarked names and often differ from the cultivar. A fine example would be the Gold Star® Juniper: Juniperus chinensis 'Bakaurea' P.P. #3801.

P.P.# and PPAF - These indicate that the plant is either patented (P.P. followed by a number) or that a patent has been applied for (PPAF). These are legal terms meaning that these plants cannot be asexually propagated by a grower, nursery or even the average gardener. Watch out for the plant police!

Unfinished Business

In the past, classification of plants (taxonomy) was done based largely on morphological analyses. However, as DNA research became more prevalent, it became obvious that some plants were more closely related than thought while others were not. This has caused many plants to be reclassified and their subsequent scientific names changed. The most glaring recent example was that of the genus Aster. At one time, there were quite a few native "asters" in North America. After the reclassification and name changes were implemented, no plants indigenous to North America remained in the genus. Some examples of recent name changes are listed below:

Blue Wood Aster: once Aster cordifolius is now Symphyotrichum cordifolium
White Wood Aster: once Aster divaricatus is now Eurybia divaricata
New York Aster: once Aster novi-belgii is now Symphyotrichum novi-belgii
New England Aster: once Aster novae-angliae is now Symphyotrichum novae-angliae

Likewise, the genus Eupatorium was "disemboweled" and plants reclassified and renamed. As more plants are examined genetically, you can bet there will be changes in their scientific names.

My advice to gardeners is to start learning the scientific names of the plants you have in your garden. As you add more plants, note their scientific names (often written on the plant tags). There are quite a few good reference books, but I'm a big fan of the "American Horticultural Society A to Z Encyclopedia of Garden Plants." This book has thousands of plants listed with great color photographs. The plants are listed alphabetically by genus with a common name cross-reference in the back.

As for pronunciation... don't worry about it. Even the most esteemed botanists will tell you it's more important to know and spell it than say it. My response when corrected on my pronunciation is hey, it's a dead language and the only authority on the subject that I recognize is Julius Caesar.