Cultivars and Ranks of Taxa According to the ICBN and ICNCP

                                                                              Jesse L. Saylor

             These are the subcategories or units of classicification according to the ICBN (International Code

 of Botanical Nomenclature, Tokyo Code, ed. by Greuter, 1994), with additions from the ICNCP (International

 Code of Nomenclature for Cultivated Plants, Cultivated Plant Code, ed. by Trehane, 1995).

            Endings are listed after each category if specified in the ICBN. More commonly used categories are in

 Red

Kingdom (-bionta)

Subkingdom

Division or Phylum (-phyta)

Subdivision or Subphylum (-phytina) [Walters and Keil use -icae, following

                                                             Cronquist, Takhtajan and Zimmerman(1966)]

Class (-opsida) [KUB uses -atae]

Subclass (-idae)

Superorder (-anae)

Order (-ales)

Suborder (-ineae)

Superfamily (-ariae)

Family (-aceae, with 8 exceptions listed)

                                                                                                                         below)

Subfamily (-oideae)

Tribe (-eae)

Subtribe (-inae)

                                                                                                                                                Genus

Genus (plural is genera)

            Subgenus

Section

Subsection

Series

Subseries

species (abbr. sp. for singular; spp. for plural)

subspecies (abbr. subsp.)

variety (abbr. var.)

`Cultivar’ or cv. Cultivar

subvariety

forma (abbr. f.)

subforma

            The Cultivar is from the ICNCP (Cultivated Plant Code) and all the other categories are

 listed in the ICBN (Tokyo Code).

            The word taxa (singular: taxon) refers to names of taxonomic groups of any rank.

            Botanical nomenclature is independent of zoological and bacteriological nomenclature.

            The principle of priority of publication means that the earliest published name is

 the most correct. The starting point for vascular plant (Spermatophyta and Pteridophyta) names

 is Linnaeus and his Species Plantarum, edition 1, May 1, 1753.

            With the family names ending in -aceae, there are 8 exceptions or names of long usage

 that are listed as valid; thus either name can be used. They are: Compositae or Asteraceae,

 Cruciferae or Brassicaceae, Gramineae or Poaceae, Guttiferae or Clusiaceae, Labiatae or

 Lamiaceae, Leguminosae or Fabaceae, Palmae or Arecaceae, Umbelliferae or Apiaceae.

            Scientific names (also called Latin names or botanical names) are binomial and are

 composed of the Genus and the species (or specific epithet) with the Genus standing by itself

 (like peoples last names) and the species being used again and again with different genera(like

 peoples first names). A genus name is only used once for plants and not repeated for other plants.

 The Genus name has meaning by itself (Ex. Acer means Maple). Genus name are always capitalized

 A species name cannot stand by itself, since the same species name is used with many genera (Ex.

 Cornus alba, Ipomoea alba, Quercus alba, Populus alba, Salix alba, etc.). Genus and species names are

 Latin names and all Latin names are italicized or underlined.

            In taxonomic and botanical literature (ncluding Hortus III, and RHS), the Genus and

 species is followed by the abbreviation of the author who named and described the plant [Ex.

 Acer rubrum L.]. If the name was revised or changed, the previous author is in parentheses

 [Actinidia arguta (Sieb. and Zucc.)Miq.]. The author name is important, especially when two

 people use the same name in describing two different plants; the author name is the only way to

 know which plant species is being referenced. This has happened in the past when two people in

 different countries described two different plants and used the same Latin name. Remember, the author

is not necessarily an authority on the plant or plants that he or she names.

            A botanical variety is found in the wild and described as such. A cultivar is found in

 cultivation. Sometimes a cultivar is called a variety or form but these are not the proper terms.

 Cultivated varieties or cultivars are not botanical varieties. However, the ranks can be similar,

 such as a white flowered selection of a blue flowered plant; which would be var. alba if first

 found in the wild, or cv. Alba if first found in cultivtion.

            Cultivar names are always capitalized, and are either written with single quotes around

 them (Ex. Acer rubrum `Red Sunset’) or as cv. before the name (Ex. Acer rubrum cv. Red

 Sunset). Cultivar names can be more than one word, but other names can only be one word.

 Cultivar names are not italicized or underlined.

            The term cultivar is derived from the words cultivated variety. In the ICNCP(Brickell

 1995) “A cultivar is a taxon that has been selected for a particular attribute or combination

 of attributes, and that is clearly distinct, uniform, and stable in its characteristics and that,

 when propagated by appropriate means, retains those characteristics.” The previous

 cultivated codes (Brickell 1980 and earlier) used this definition: “The international term

 cultivar denotes an assemblage of cultivated plants which is clearly distinguished by any

 characters (morphological, physiological, cytological, chemical, or others), and which, when

 reproduced (sexually or asexually), retains its distinguishing characters.” The ICNCP also

 states: “The words “variety” and “form” (or their equivalent in other languages) must not be used

 as synonymns for the word cultivar when fulfilling the Articles of this Code, nor in translations of

 this Code.” This also applies to the use of the term “strain”, since it has been widely used with

 different meanings.

             Clones (which are asexually propagated from any part of a plant), may be given cultivar

 names. Clones derived from aberrant (abnormal) growth may be given cultivar names. Graft-

chimaeras (composed of tissues from two different plants and originated by grafting) may be

 given cultivar names (Ex. Syringa `Correlata’, which combines tissues from Syringa x chinensis

 and Syring vulgaris). F₁ hyrids (the result of a repeatable single cross between two pure-bred

 lines), cultivar groups [Ex. Tulipa Darwin Group; Solanum tuberosum ‘Desiree’ (Red-skinned

 Group); the group name is in parentheses if a specific cultivar is listed], and a number of other

 categories are specifically listed as items that can be given cultivar names.

             The term Grex (a hybrid group of known parentage) is mentioned, but the code specifically

 indicates that it should not be used for any plants except orchids, where it has been in use for some time.

 However, Grex is now used by some authors for more than just orchids.

            Hybrids are discussed in the ICBN, and are indicated by the multiplication sign x, or by

 the addition of the prefix notho- to the term denoting the rank of the taxon. Intergeneric hybrids

 (between two different genera) have the x before the name (Ex. X Mahoberberis). Interspecific

 hybrids (between two or more species) have the x before the epithet of species name (Ex. Mentha

 x piperita). Also note that the x is not underlined or italicized like the Latin names.

            The ICBN includes lists of family names and genus names that are conserved over the

 oldest or most valid name. These lists are established to provide some stability in names of long

 usage, and to eliminate specific nomenclatural problems.