Plant taxonomy

Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (the science that finds, describes, classifies, and names living things).

Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two. In practice, "Plant systematics" involves relationships between plants and their evolution, especially at the higher levels, whereas "plant taxonomy" deals with the actual handling of plant specimens. The precise relationship between taxonomy and systematics, however, has changed along with the goals and methods employed.

Plant taxonomy is well known for being turbulent, and traditionally not having any close agreement on circumscription and placement of taxa. See the list of systems of plant taxonomy.

Identification, classification and description of plants

Three goals of plant taxonomy are the identification, classification and description of plants. The distinction between these three goals is important and often overlooked.

1.Plant identification is a determination of the identity of an unknown plant by comparison with previously collected specimens or with the aid of books or identification manuals. The process of identification connects the specimen with a published name. Once a plant specimen has been identified, its name and properties are known.

2.Plant classification is the placing of known plants into groups or categories to show some relationship. Scientific classification follows a system of rules that standardizes the results, and groups successive categories into a hierarchy. For example, the family to which the lilies belong is classified as follows:

The classification of plants results in an organized system for the naming and cataloging of future specimens, and ideally reflects scientific ideas about inter-relationships between plants. The set of rules and recommendations for formal botanical nomenclature, including plants, is governed by the International Code of Nomenclature for algae, fungi, and plants abbreviated as ICN.

3.Plant description is a formal description of a newly discovered species, usually in the form of a scientific paper using ICN guidelines. The names of these plants are then registered on the International Plant Names Index along with all other validly published names.

Classification systems

See List of systems of plant taxonomy

Online databases

See Category: Online botany databases

See also

External links

Botanical name

A botanical name is a formal scientific name conforming to the International Code of Nomenclature for algae, fungi, and plants (ICN) and, if it concerns a plant cultigen, the additional cultivar or Group epithets must conform to the International Code of Nomenclature for Cultivated Plants (ICNCP). The code of nomenclature covers "all organisms traditionally treated as algae, fungi, or plants, whether fossil or non-fossil, including blue-green algae (Cyanobacteria), chytrids, oomycetes, slime moulds and photosynthetic protists with their taxonomically related non-photosynthetic groups (but excluding Microsporidia)."The purpose of a formal name is to have a single name that is accepted and used worldwide for a particular plant or plant group. For example, the botanical name Bellis perennis denotes a plant species which is native to most of the countries of Europe and the Middle East, where it has accumulated various names in many languages. Later, the plant was introduced worldwide, bringing it into contact with more languages. English names for this plant species include: daisy, English daisy, and lawn daisy. The cultivar Bellis perennis 'Aucubifolia' is a golden-variegated horticultural selection of this species.

Botanical nomenclature

Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature then provides names for the results of this process. The starting point for modern botanical nomenclature is Linnaeus' Species Plantarum of 1753. Botanical nomenclature is governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which replaces the International Code of Botanical Nomenclature (ICBN). Fossil plants are also covered by the code of nomenclature.

Within the limits set by that code there is another set of rules, the International Code of Nomenclature for Cultivated Plants (ICNCP) which applies to plant cultivars that have been deliberately altered or selected by humans (see cultigen).

Class (biology)

In biological classification, class (Latin: classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order.


A genus (, pl. genera ) is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

E.g. Panthera leo (lion) and Panthera onca (jaguar) are two species within the genus Panthera. Panthera is a genus within the family Felidae.The composition of a genus is determined by a taxonomist. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful:

monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should clearly demonstrate both monophyly and validity as a separate lineage).

reasonable compactness – a genus should not be expanded needlessly; and

distinctness – with respect to evolutionarily relevant criteria, i.e. ecology, morphology, or biogeography; DNA sequences are a consequence rather than a condition of diverging evolutionary lineages except in cases where they directly inhibit gene flow (e.g. postzygotic barriers).Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera.


A herbarium (plural: herbaria) is a collection of preserved plant specimens and associated data used for scientific study.The specimens may be whole plants or plant parts; these will usually be in dried form mounted on a sheet of paper (called "exsiccatae") but, depending upon the material, may also be stored in boxes or kept in alcohol or other preservative. The specimens in a herbarium are often used as reference material in describing plant taxa; some specimens may be types.

The same term is often used in mycology to describe an equivalent collection of preserved fungi, otherwise known as a fungarium. A xylarium is a herbarium specialising in specimens of wood. The term hortorium (as in the Liberty Hyde Bailey Hortorium) has occasionally been applied to a herbarium specialising in preserving material of horticultural origin.

History of plant systematics

The history of plant systematics—the biological classification of plants—stretches from the work of ancient Greek to modern evolutionary biologists. As a field of science, plant systematics came into being only slowly, early plant lore usually being treated as part of the study of medicine. Later, classification and description was driven by natural history and natural theology. Until the advent of the theory of evolution, nearly all classification was based on the scala naturae. The professionalization of botany in the 18th and 19th century marked a shift toward more holistic classification methods, eventually based on evolutionary relationships.

International Association for Plant Taxonomy

The International Association for Plant Taxonomy (IAPT) promotes an understanding of plant biodiversity, facilitates international communication of research between botanists, and oversees matters of uniformity and stability in plant names. The IAPT was founded on July 18, 1950 at the Seventh International Botanical Congress in Stockholm, Sweden. Currently, the IAPT headquarters is located in Bratislava, Slovakia. Its current president, since 2017, is Patrick S. Herendeen (Chicago Botanic Garden); vice-president is Gonzalo Nieto Feliner (Real Jardín Botánico, Madrid); and secretary-general is Karol Marhold (Plant Science and Biodiversity Centre, Slovak Academy of Sciences, Bratislava).

Both the taxonomic journal Taxon and the series Regnum Vegetabile are published by the IAPT. The latter series includes the International Code of Nomenclature for algae, fungi, and plants, Index Nominum Genericorum, and Index Herbariorum.

International Code of Nomenclature for algae, fungi, and plants

The International Code of Nomenclature for algae, fungi, and plants (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "traditionally treated as algae, fungi, or plants". It was formerly called the International Code of Botanical Nomenclature (ICBN); the name was changed at the International Botanical Congress in Melbourne in July 2011 as part of the Melbourne Code which replaced the Vienna Code of 2005.

The current version of the code is the Shenzhen Code adopted by the International Botanical Congress held in Shenzhen, China, in July 2017. As with previous codes, it took effect as soon as it was ratified by the congress (on 29 July 2017), but the documentation of the code in its final form was not published until 26 June 2018.

The name of the Code is partly capitalized and partly not. The lower-case for "algae, fungi, and plants" indicates that these terms are not formal names of clades, but indicate groups of organisms that were historically known by these names and traditionally studied by phycologists, mycologists, and botanists. This includes blue-green algae (Cyanobacteria); fungi, including chytrids, oomycetes, and slime moulds; photosynthetic protists and taxonomically related non-photosynthetic groups. There are special provisions in the ICN for some of these groups, as there are for fossils.

The ICN can only be changed by an International Botanical Congress (IBC), with the International Association for Plant Taxonomy providing the supporting infrastructure. Each new edition supersedes the earlier editions and is retroactive back to 1753, except where different starting dates are specified.For the naming of cultivated plants there is a separate code, the International Code of Nomenclature for Cultivated Plants, which gives rules and recommendations that supplement the ICN.

List of systems of plant taxonomy

This list of systems of plant taxonomy presents "taxonomic systems" used in plant classification.

A taxonomic system is a coherent whole of taxonomic judgments on circumscription and placement of the considered taxa. It is only a "system" if it is applied to a large group of such taxa (for example, all the flowering plants).

There are two main criteria for this list. A system must be taxonomic, that is deal with a large number of plants, by their botanical names. Secondly it must be a system, i.e. deal with the relationships of plants. Although thinking about relationships of plants had started much earlier (see history of plant systematics), such systems really only came into being in the 19th century, as a result of an ever-increasing influx from all over the world of newly discovered plant species. The 18th century saw some early systems, which are perhaps precursors rather than full taxonomic systems.

A milestone event was the publication of Species Plantarum by Linnaeus which serves as the starting point of binomial nomenclature for plants. By its size this would qualify to be on this list, but it does not deal with relationships, beyond assigning plants into genera.

Note that a system is not necessarily monolithic and often goes through several stages of development, resulting in several versions of the same system. When a system is widely adopted, many authors will adopt their own particular version of the system. The Cronquist system is well known for existing in many versions.

Plants of the World Online

Plants of the World Online is an online database published by the Royal Botanic Gardens, Kew. It was launched in March 2017 with the ultimate aim being "to enable users to access information on all the world's known seed-bearing plants by 2020". The initial focus was on tropical African Floras, particularly Flora Zambesiaca, Flora of West Tropical Africa and Flora of Tropical East Africa.

Section (biology)

In biology a section (Latin: Sectio) is a taxonomic rank that is applied differently between botany and zoology.

Section (botany)

In botany, a section (Latin: sectio) is a taxonomic rank below the genus, but above the species. The subgenus, if present, is higher than the section, and the rank of series, if present, is below the section. Sections may in turn be divided into subsections.Sections are typically used to help organise very large genera, which may have hundreds of species. A botanist wanting to distinguish groups of species may prefer to create a taxon at the rank of section or series to avoid making new combinations, i.e. many new binomial names for the species involved.Examples:

Lilium section Martagon Rchb. are the Turks' cap lilies

Plagiochila aerea Taylor is the type species of Plagiochila sect. Bursatae

Series (botany)

In botany and plant taxonomy, a series is a subdivision of a genus, a taxonomic rank below that of section (and subsection) but above that of species.Sections and/or series are typically used to help organize very large genera, which may have hundreds of species.


In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus.

In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the generic name and the specific epithet: e.g. the tiger cowry of the Indo-Pacific, Cypraea (Cypraea) tigris Linnaeus, which belongs to the subgenus Cypraea of the genus Cypraea. However, it is not mandatory, or even customary, when giving the name of a species, to include the subgeneric name.

In the International Code of Nomenclature for algae, fungi, and plants (ICNafp), the subgenus is one of the possible subdivisions of a genus. There is no limit to the number of divisions that are permitted within a genus by adding the prefix "sub-" or in other ways as long as no confusion can result. The secondary ranks of section and series are subordinate to subgenus. An example is Banksia subg. Isostylis, a subgenus of the large Australian genus Banksia. The ICNafp requires an explicit "connecting term" to indicate the rank of the division within the genus. Connecting terms are usually abbreviated, e.g. "subg." for "subgenus", and are not italicized.

In zoological nomenclature, when a genus is split into subgenus, the originally described population is retained as the "nominotypical subgenus" or "nominate subgenus", which repeats the same name as the genus. For example, Panthera (Panthera) pardus, a leopard. In botanical nomenclature, the same principle applies, although the terminology is different. Thus the subgenus that contains the original type of the genus Rhododendron is Rhododendron subg. Rhododendron. Such names are called "autonyms".

Taxon (journal)

Taxon is a bimonthly peer-reviewed scientific journal covering plant taxonomy. It is published by Wiley on behalf of the International Association for Plant Taxonomy, of which it is the official journal. It was established in 1952 and is the only place where nomenclature proposals and motions to amend the International Code of Nomenclature for algae, fungi, and plants (except for the rules concerning fungi) can be published. The editor-in-chief is Dirk C. Albach (University of Oldenburg).

The Plant List

The Plant List is a list of botanical names of species of plants created by the Royal Botanic Gardens, Kew and the Missouri Botanical Garden and launched in 2010. It was intended to be a comprehensive record of all known names of plant species over time.

In October 2012, the follow-up project World Flora Online was launched with the aim to publish an online flora of all known plants by 2020.There is a complementary project called the International Plant Names Index, in which Kew is also involved. The IPNI aims to provide details of publication and does not aim to determine which are accepted species names. Newly published names are automatically added from IPNI to the World Checklist of Selected Plant Families, a database which underlies the Plant List.

Tribe (biology)

In biology, a tribe is a taxonomic rank above genus, but below family and subfamily. It is sometimes subdivided into subtribes. By convention, all taxonomic ranks above genus are capitalized, including both tribe and subtribe.

In zoology, the standard ending for the name of a zoological tribe is "-ini". Examples include the tribes Caprini (goat-antelopes), Hominini (hominins), Bombini (bumblebees), and Thunnini (tunas). The tribe Hominini is divided into subtribes by some scientists; subtribe Hominina then comprises "humans". The standard ending for the name of a zoological subtribe is "-ina".

In botany, the standard ending for the name of a botanical tribe is "-eae". Examples include the tribes Acalypheae and Hyacintheae. The tribe Hyacintheae is divided into subtribes, including the subtribe Massoniinae. The standard ending for the name of a botanical subtribe is "-inae".

In bacteriology, the form of tribe names is as in botany, e.g., Pseudomonadeae, based on the genus name Pseudomonas.

Variety (botany)

In botanical nomenclature, variety (abbreviated var.; in Latin: varietas) is a taxonomic rank below that of species and subspecies, but above that of form. As such, it gets a three-part infraspecific name. It is sometimes recommended that the subspecies rank should be used to recognize geographic distinctiveness, whereas the variety rank is appropriate if the taxon is seen throughout the geographic range of the species.

World Checklist of Selected Plant Families

The World Checklist of Selected Plant Families (usually abbreviated to WCSP) is an "international collaborative programme that provides the latest peer reviewed and published opinions on the accepted scientific names and synonyms of selected plant families." Maintained by the Royal Botanic Gardens, Kew, it is available online, allowing searches for the names of families, genera and species, as well as the ability to create checklists.

The project traces its history to work done in the 1990s by Kew researcher Rafaël Govaerts on a checklist of the genus Quercus. Influenced by the Global Strategy for Plant Conservation, the project expanded. As of January 2013, 173 families of seed plants were included. Coverage of monocotyledon families is complete; other families are being added.There is a complementary project called the International Plant Names Index (IPNI), in which Kew is also involved. The IPNI aims to provide details of publication and does not aim to determine which are accepted species names. After a delay of about a year, newly published names are automatically added from the IPNI to the WCSP. The WCSP is also one of the underlying databases for The Plant List, created by Kew and the Missouri Botanical Garden, which was unveiled in 2010.

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