Botanical Nomenclature

Botanical nomenclature is the formal naming of plants, from a scientific point of view. It has a long history, going back perhaps to Theophrastos, but anyway back to the period when Latin was the scientific language throughout Europe. The keystone event was Linnaeus’ adoption of binary names for plant species in his Species Plantarum (1753). This gave every plant species a name which remained the same no matter what other species were placed in the genus, and thus separated taxonomy from nomenclature. These species names of Linnaeus together with names for other ranks, notably the rank of family (not used by Linnaeus), can serve to express a great many taxonomic viewpoints.

In the nineteenth century it became increasingly clear that there was a need for rules to govern scientific nomenclature and initiatives were taken to come to a body of laws. These were published in successively more sophisticated editions. For plants the key dates are 1867 (lois de Candolle), 1906 (International Rules of Botanical Nomenclature, 'Vienna Rules') and 1952 (International Code of Botanical Nomenclature, 'Stockholm Code').

Another development was insight into delimitation of the concept 'plant'. Linnaeus held a much wider view of what a plant is than is acceptable today. Gradually more and more groups of organisms are recognised as being independent of plants. Nevertheless the formal names of most of these organisms are governed by the International Code of Botanical Nomenclature (ICBN), even today. A separate Code was adopted to govern the nomenclature of Bacteria, the ICNB.

At the moment all formal botanical names are governed by the ICBN. Within the limits set by the ICBN there is a separate set of rules, the International Code of Nomenclature for Cultivated Plants (ICNCP). Within the group of plants that have been deliberately altered or selected by humans (see cultigen) there are those that require separate recognition, known as cultivars. Within the limits set by the ICNCP there is a separate set of rules for orchid hybrids.

Nomenclature refers to the naming of things. Botanical nomenclature is (surprise) about naming plants. Bear in mind that plant names refer to abstract entities - the collection of all plants (past, present, and future) that belong to the same group. As you will recall, taxonomy is about grouping. Botanical nomenclature is about applying names to taxonomic groups.

Scientific names of plants reflect the taxonomic group to which the plant belongs. One must first decide on the groups to be recognized; only then does one start to be concerned about assigning an appropriate name to the plant. Common names, at least those that are genuinely common names, usually reflect some conspicuous or valuable characteristic of the plant, not its taxonomic group. The following comments are about scientific names.

Scientific names are never misleading. No matter where you are, every plants has only one correct name. so long as its taxonomic treatment is not in dispute. This last is a major reservation, but we can ignore it for now. The universality of scientific names means that even English speaking people can find out what species grow in China or Saudi Arabia by reading a technical flora of these countries. Not only are the names the same, they are always written in the Latin alphabet (which is the same alphabet as these notes).

There is as little point about worrying over the 'correct' pronunciation of scientific names as there is in worrying over which is the correct pronunciation of English words. It may be difficult to recognize a scientific name if it is spoken by someone from another part of the world BUT one can always recognize it when it is written out. In this, scientific names are no different from other words. Think how hard it can be to understand different versions of English. Nevertheless, it is advantageous to use the same pronunciation as the other people you work with. Just be prepared to modify your pronunciation if you move to another part of the world.

Taxonomy refers to forming groups. Plants that belong to the same group have the same name. The taxonomic decisions concerning how a group is to be treated (what goes in the group, what rank it should be recognized as ) MUST be made before it can be assigned a name. It does not matter how you decide what its affinities are (unless, of course, you want others to support and use your treatment), but you must make these decisions before you can decide on an appropriate name for the group. So remember, taxonomy first. If people are going to communicate around the world, there needs to be an internationally accepted system of nomenclature. Creating such a system was not, and is not, an easy task. It was not until 1930 that agreement was reached on an International Code had become standard around 1753. There were, however, many areas where there was widespread agreement in practice, with some of the practices dating back to before Linnaeus. For reasons that you will learn later, Linnaeus is taken as the starting point for botanical nomenlcature. Let's consider for a moment some of the areas of agreement that existed before there wasformal agreement on an International Code of Botanical Nomenclature.

Towards an International Code
Pre-Linnaean Practices
1) Names were formed like Latin words. The reason is quite straightforward; Latin was the common language among all European peoples - and plant taxonomy as we know it has its origins in Europe. 2) Once a name had been attached to a plant group, it should not be given another name.

3) When commenting on how a name was to be interpreted, one should list the names of others that had used it.

4) It helps to mention some specimens that one has seen.

The first attempt at developing an international agreement was made in Paris in 1867. At this meeting, it was decided that a) the first edition of Linnaeus' Species Plantarum, which was published in 1752, would serve as the starting point of botanical nomenclature and b) if two names had been given to the same plant group, the older name would be the correct name. In addition, various rules were laid down as to what was required to valid publication - a phrase that means "published in such a manner that the name counts". For instance, publication of new names in horticultural catalogs used to be acceptable, but it is not any longer.

Other Codes
In 1892, a group of US botanists held a meeting in Rochester at which they presented some additions and modifications that they considered more objective (a great phrase in science). Among the changes that they proposed were that a) when publishing a new name one should cite at least one herbarium specimen representing the plant group concerned and b) that, when a species was moved from one genus to another it should, if possible, keeps its specific epithet (it is not possible if that epithet has already been used for another species in the new genus). Some of the new rules conflicted with those proposed in Paris, and the modified version being used at Kew, a major taxonomic center in England.

Agreement, at last
In 1930, taxonomists finally agreed on a single International Code of Botanical Nomenclature. This Code is revised every 6 years, but the goals of all the revisions are always to achieve stability in scientific nomenclature and or to clarify problems. The revisions are published in Taxon, the journal of the International Society of Plant Taxonomists, then voted on at a meeting that is held immediately prior to an International Botanical Congress. The last edition of the Code was published in 2000. There is a copy in the herbarium.

Limitations of the Code
Before considering what the Code says, it is important to know what it does, and does not, attempt to do.

It DOES state what to do when you wish to assign a new name to a plant group, how the names of plant groups are to be informed, how to inform people about new names, and how to choose between two (or more) names that have been given to the same plant group.

It DOES NOT provide any information on how to decide whether a group of plants should be given a scientific name or what rank a group should have. These activities are taxonomic, not nomenclatural.

Remember: Taxonomy comes before nomenclature.

International Code of Botanical Nomenclature (ICBN) »

International Code of Nomenclature for Cultivated Plants (ICNCP) »

If you have to publish a new name or combination, the Code requires that you follow certain rules (which it calls articles). The key requirements are that:
1. The new name or combination be published in a normal botanical outlet (not the Herald Journal or Statesman), copies of which are sent to at least two botanical institutions.
2. If the name is for a new taxon, the distinguishing characteristics of the taxon, and preferably a full description, must be given in Latin and a holotype specified.
3. If the name is simply a new combination, perhaps reflecting the transfer of a species from one genus to another or its demotion to a subspecies, there must be a clear and complete reference to the place where the original name was first published.

1. Discovery of an older name for the taxon that has been overlooked. In the last decade, it has become possible to conserve the name actually being used if one can show that the earlier name has never become established. This is a nomenclatural, not taxonomic reason, for changing a name.
2. Discovery that the name being used for a particular taxon had been applied earlier to some other taxon. This is a nomenclatural, not taxonomic reason, for changing the name.
3. A decision that a species belongs in a different genus, or that a taxon needs to be split, or that the rank of the taxon needs to be changed. These are all taxonomic decisions.

Most name changes reflect taxonomic decisions, but people that do not agree with the decision may continue to use the existing name. This is what non-taxonomists find frustrating, if not infuriating. Such people often become even more frustrated when told that there is no set of criteria nor any governing board that determines at what rank a taxon should be recognized at, or what its boundaries should be. There are stronger and weaker arguments, but there is not even complete agreement on which are strong arguments and which are weak. Taxonomy is not a field for those that require certainty in their life.

Other Names
Plants are often known by many different names. The names Convolvulus arvensis; Bindweed, Field bindweed, Common bindweed, Small bindweed,
Morning glory, and Liseron des champs all refer to the same species. The scientific name is Convolvulus arvensis. The other names are what are called common names or vernacular names. I prefer the phrase 'vernacular name' because many so-called common names are simply names constructed to satisfy the demand for a name in a familiar language - they are not names in common use.

Although many people like 'common names', there are many problems associated with them. For instance, Indian ricegrass (Achnatherum hymenoides) is not a close relative of either rice or wild rice (two very different species), but it was used for food by Native Americans and looks something like short grain rice. I regard it as a genuine common name - among English speaking people. But the species was an important component of the diet of the Native Americans in Utah and the west. I rather doubt that it is called Indian Ricegrass in any Native American language.

Sometimes, the common name is the same, or partly the same as the scientific name. Many of you probably have no problem understanding Penstemon and Delphinium, but both of these are scientific names. If you grew up in England or Australia, you would also be familiar with Capsicum as a common name, but in North America the commonly encountered species of Capsicum are called bell peppers or chili peppers. Despite their American names, species of bell peppers and chili peppers are more closely related to potatoes, eggplant, and nightshades than the kind of pepper that we use in pepper grinders.

Problems arise when vernacular names have been created based on scientific names, but the meaning of the scientific name changes. For instance, all species in the genus Agropyron were given common names that incorporated the word 'wheatgrass'. The trouble is that most of these species have since been kicked out of Agropyron. It is not a huge problem, but it does point up how artificial so many 'common names' are.

Another problem with common names is that they may apply to more than one species. Corn used to the name for the grain most used for flour. In England, corn meant wheat; in Scotland, it meant rye or barley; in these two countries what Americans call corn was known as maize. With the increasing dominance of American English, corn is now generally interpreted as meaning Zea mays - otherwise known as maize. Similarly 'Bluebell' forms part, or all, of the name of many different plants. I learned of it as referring to monocots that are sold here as Wood hyacinths. In Scotland, it applies to what I would call a Harebell. but the northern Utah flora refers to as Arctic bellflower. This same work gives Bluebell as the common name for Mertensia, a third genus and a third family. The USDA PLANTS database lists 18 different species as having Bluebell as part of their common name.

Even in one's own language, common names can be rather obscure. Do you know what plant is meant by Jack-in-the-Pulpit? Actually, that one is not bad. But how about "Welcome home husband no matter how drunk you may be"? Yes, I have seen it listed as a common name. Clearly the people that use it are not bothered by long names. And no, I have never met anyone that uses it.

Common names have local value; scientific names have universal value. in this class, we focus on scientific names.

Official Names
In some countries, one or more government agencies creates plant names in the country's native or official language which they require their employees and contract employees to use. Some of these names are what I would refer to as the truly common names, but many are just extensions of a true common name to other species, often by translating the specific epithet. Official names can be useful in talking to non-botanists, but the result is often a parallel system of nomenclature. The U. S. A. is one such country. Indian ricegrass appears to be a genuine common name, that is, one that ordinary people coined and used, for the species that used to be known as Oryzopsis hymenoides. Unfortunately, the USDA decided that all species of the genus Oryzopsis should be called ricegrasses so the official name of O. kingii became King Ricegrass and O. asperifolia became Roughleaved ricegrass although neither of these species has ever been used as a source food for humans. The problem with this approach to creating official names (which are generally called common names) is that taxonomic study shows that neither Oryzopsis hymenoides nor O. kingii belongs in Oryzopsis. Oryzopsis hymenoides is now placed in either Achnatherum or Stipa (there is taxonomic disagreement) while O. kingii is placed in the genus Ptilagrostis. Should the official name of P. kingii be changed from King Ricegrass? If so, to what?

There are other problems with having official names. For instance, several years ago, the old Soil Conservation Service sent out an updated list of approved common names for Utah's plants. Among other idiocies, it was proposed that people should stop referring to penstemons (unless using a scientific name) and start referring to the species involved as beardtongues even thought the vast majority of the official names (which were called common names) were basically a translation of the binomial. In my opinion, it makes more sense to teach people to refer to Eatons Penstemon rather than Eatons Beardtongue. At least that way they learn half the scientific name.

Relationship to taxonomy

Botanical nomenclature is closely linked to plant taxonomy, and botanical nomenclature serves plant taxonomy, but nevertheless botanical nomenclature is separate from plant taxonomy. Botanical nomenclature is merely the body of rules prescribing which name applies to that taxon (see correct name) and if a new name may (or must) be coined.

Plant taxonomy is an empirical science, a science that determines what constitutes a particular taxon (taxonomic grouping, plural: taxa): e. g. "What plants belong to this species? " and "What species belong to this genus? "). Where taxonomists differ in opinion more than one name may be used for one and the same plant. Within any taxonomic viewpoint only one name can be correct, but somebody holding a different taxonomic viewpoint may be using a different name, although for him too there is only one correct name (in his taxonomic viewpoint).

This means that in case of confusion:
  • If confusion is nomenclatural (for example an older name is discovered which has priority and threatens to displace a well-known name), the Code offers means to set things right (at least sometimes): see conservation.
  • If confusion is taxonomic (taxonomists differ in opinion on the circumscription or the relationships of taxa), then only more scientific research can settle this.