Plant Taxonomy and Nomenclature
Plant taxonomy is the classifying and grouping of closely related plants into a particular taxon (plural: taxa). The description of the plants within a taxon is called its circumscription. Botanical nomenclature is the body of rules for determining which name applies to a particular taxon, and occasionally if a new name is needed. Modern botanical nomenclature started with Carl Linnaeus and his 1753 publication, Species Plantarum (Latin for "The Species of Plants"). It is now governed by the International Code of Nomenclature for algae, fungi and plants (ICN).
Plant names have many parts, each indicating if and how the taxon is related to other taxa.
Species Name – A two-part, Latinized name consisting of the genus name and specific epithet, representing the basic unit of scientific classification. (Example: Acer saccharum is the species name of sugar maple, "Acer" is the genus and "saccharum" is the specific epithet.)
Infraspecific Rank and Name – These Latinized parts of the botanic name are used to describe naturally occuring variations from the typical species characteristics, and thus are not used in the vast majority of plant names. There are three ranks of infraspecific names, so when an infraspecific name is given, its rank classification must also be provided.
- Subspecies – Describes a collection of plants within a specific geographic portion of the overall range of the species, with slightly different characteristics compared to the straight species. Abbreviated as "subsp." (Example: Cornus kousa subsp. chinensis refers to certain kousa dogwoods specifically originating from parts of China that have differences separating them from kousa dogwood trees elsewhere in its range.)
- Variety – Describes a collection of plants with naturally occurring and stable differences compared to the straight species. These differences are not limited to a specific geographic area, but rather are found throughout the overall range of the species. Abbreviated as "var." (Example: Cornus florida var. rubra are flowering dogwood trees with pink instead of white bracts.)
- Forma – Describes a collection of plants with very slight differences compared to the straight species. These differences are found throughout the overall range of the species (not geographically isolated) and are usually but not always environmentally induced (rather than genetically). Abbreviated as "f." (Example: Gleditsia triacanthos f. inermis are honeylocust trees naturally without thorns.)
Cultivar Name – Short for "cultivated variety," a collection of plants being selected and cultivated for particular, distinct, uniform and stable attributes. Not all plants will have a cultivar name. (Example: Acer saccharum 'Green Mountain' is an improved sugar maple.)
Common Name – Any name for a plant that is not its formal, scientific name. One plant may have different common names in different localities, and because of this one common name may identify several different plant species throughout the world. Conversely, each scientific name uniquely identifies a single plant species around the world. (Example: sugar maple, rock maple, or hard maple are all common names of the species Acer saccharum.)
Trademark Name – Sometimes a nursery will develop and trademark a more marketable name for a new cultivar. (Example: Prairie Dream® is the registered trademark name of the paper birch cultivar Betula papyrifera 'Varen'.)
Name Changes (synonyms)
By the rules of nomenclature, no plant can have more than one botanical name. If a plant had accidentally been given two names, a correction is needed. Generally the first name published becomes the accepted (correct) name and any other names are listed as synonym (incorrect) names.
Also, if it is determined (such as through genetic testing) that a plant had been incorrectly classified, the research settles on a new accepted name and the former names thus become synonyms.
Just like accepted names, synonym names cannot describe two separate plants, so they will not be reused.