Nomenclatural codes

The International Code of Nomenclature for algae, fungi and plants (icn)

Carl Linnaeus
by Henrik Hollander
The ICN sets out principles, rules and recommendations for naming plants according to the binomial system employed by Linnaeus in his Species Plantarum (1753).  It makes provisions for naming taxa (a general word for all units of biological classification) at the levels of species, genus, family and above and, within species, for a number of infraspecific ranks, notably subspecies, varietas and forma. Names for hybrids between different taxa are also addressed. In addition to stipulations regarding the formation of names, the ICN also states the requirements of valid publication and presents a system for dealing with issues of priority and synonymy.  

Though some basic elements are deeply embedded in the ICN, other aspects are subject to amendment and adjustment according to changing ideas in taxonomy and developments in understanding and technology.  However, the ICN can only be revised at an International Botanical Conference (IBC).  The 19th IBC took place in Shenzhen, China in July 2017.

The International Code of Nomenclature for Cultivated Plants (ICNCP)

Dahlia 'Nenekazi'
© RHS
Many plants in gardens require no other name than that which would be attributed to them if they were found growing in the wild.  However, where plants which possess distinct, desirable characteristics, which can be maintained through a process of controlled propagation, are selected or bred, some additional means of identification and communication is required.  

Prior to the publication of the first edition of the ICNCP in 1953, the unregulated application of names to cultivated plants led to widespread confusion and a lack of clarity regarding the status implied by a name.

The ICNCP (sometimes called the Cultivated Plant Code) offers principles, rules and recommendations concerning the formation, establishment and styling of the names of cultivars, Groups and grexes. It also contains sections on registration and nomenclatural standard specimens.

Over the years the ICNCP has been altered and added to following International Symposia on the Taxonomy of Cultivated Plants. The latest version (the 9th edition) was published in 2016 following the Symposium in Beijing, China in July 2013.

Amending the Nomenclatural Code

The idea is widely held that decisions concerning the rules by which cultivated plants are named are made by remote and inaccessible bodies but really the process is an open one and anybody can have their say.

Proposals to amend the ICNCP can be submitted for publication in the Journal of Cultivated Plant Diversity (formerly Hanburyana), or can be emailed to icncp@rhs.org.uk. Code proposals should identify which article is being addressed and outline in a logical sequence the perceived weakness which it contains, the amendment being suggested and the argument for its adoption.

These proposals are discussed and considered at international symposia for cultivated plant taxonomy which occur every few years at different venues across the world. 

At the end of each symposium a final decision is taken over whether to accept or reject each proposal by the IUBS (International Union of Biological Sciences) International Commission for the Nomenclature of Cultivated Plants.