Understanding plant names. 

Plant names exist to help communicate some information about that plant and to identify it as distinct from others.  Our resource covers the basics of plant naming, to help you better understand the plants you grow, and to assist users of our plant records database, Persephone.

For a full guide on the correct construction and use of plant names, please refer to the International Code of Nomenclature for algae, fungi, and plants (Shenzhen code).

The National Plant Collection holder for Tradescantia has also produced some excellent articles written in plain English, available through the Tradescantia UK website.

This work has been supported by the National Lottery Heritage Fund, with thanks to National Lottery players.  Text content is licenced under CC BY 4.0.

Common names vs scientific names

Common names are those familiar names for plants that you might use in general conversation.  They can be wonderfully evocative, like monkshood, bleeding heart and the monkey puzzle tree.

However, common names aren't universally helpful for the identification and description of plants!

The drawbacks of common names include:

• They differ across regions and change depending on language
• The same name might be used to refer to more than one plant
• Plants often have several different common names
• They can be misleading, for example many plants commonly known as "lily" are not related to true lilies, or to each other (voodoo lily, calla lily, lily-of-the-valley...)
• They can sometimes use outdated and even offensive language

Taxonomy and nomenclature

Taxonomy is the study of how things are categorised and nomenclature is the study of how they are named.  In biology, these two studies tend to work in tandem, as assigning names can help us to comprehend groups of living things.  It is important to remember that the discrete categories humans assign to life can vary from the fluid and complex reality of nature!

One means of understanding the relatedness of living things is through the framework of taxonomic ranking.  The ranking system goes from more general to more specific at its base.

When discussing plants in horticulture, we generally focus on the more specific ranks toward the bottom of the framework: family, genus and species.

A species is the main unit used when describing individual kinds of living things.  A distinct species is most often understood as a group of living things which can actually or potentially breed in nature, and produce viable (fertile) offspring.  However, this definition does not universally apply, particularly with plants, and there are several different concepts around the idea of a "species".  To find out more, Berkeley University has a good beginner's guide to species concepts.

Genus and family

The genus is a group of species which are clearly and closely related, i.e. they all share a common ancestor.  They will share some traits which indicate their relatedness, though what these traits are will vary, depending on the genus.  Flowers/reproductive structures are usually a better indicator of evolutionary relationships than the other parts of a plant.

The number of species in a genus can vary but efforts are made to keep this reasonable, though there are some exceptions, like the genus Euphorbia (spurges) which has over 3000 species.  Where genera are large, they can be broken down into subgenera (subg.) or sections (Sect.).

Genera (plural of genus) are grouped into larger groups of related plants called families.  In plants, family names follow the rule of ending in the suffix -aceae (with a few accepted older names remaining in use which do not follow this role).  Generally, the family name is formed from the most characteristic genus (type genus) within that family and this suffix, for example Iridaceae (the Iris family).

When writing a species name, the genus always begins with a capital, and the specific epithet follows in lowercase. The whole species name is written in italics (publications produced before modern printers may instead use an underline).

Genus and specific epithet: the binomial name

Scientific names in biology (including botanical names) follow a modification of the nomenclatural system developed by Swedish naturalist Carl Linnaeus in his 18th century works.  This is the binomial naming system.  Under this system, each basic unit of a living thing is assigned a binomial species name.  This is comprised of two parts, firstly the genus, followed by the specific epithet.

Binomial names are given by the author when a plant is correctly published and can be an interesting topic of study in themselves!  They often carry some information about the plant or its author, as they are usually either:

• Descriptive, based on a trait of the plant, e.g. Acer palmatum with its palmate leaves
• Geographic, based on a region or habitat, e.g. Agave utahensis from the US state of Utah
• Honorific, given in celebration of someone, e.g. Alstroemeria, genus named for Swedish naturalist Clas Alströmer

If the etymology of plant names interests you, there are many publications on the subject and you can search the Dave's Garden Botanary online.

Infraspecific ranks

Plants can be separated out further at a level below the species, if the plant has distinct variations of taxonomic note.  These are known as infraspecific ranks.  Plants can have multiple different infraspecific ranks in combination with each other, but only one of each.

Infraspecific rank names are found after the specific epithet, and are denoted by a connecting term, depending on the rank.

An example of a plant name with an infraspecific rank, in this case a subspecies of the silver birch Betula pendula, Betula pendula subsp. mandshurica (common name: Japanese white birch).

Subspecies

Subspecies (abbreviated to subsp.) distinctions are usually made on the basis of geographical distinctiveness within a species.

For example, Beta vulgaris subsp. adanensis is a subspecies of beet which is native to the eastern Mediterranean.

Variety

Not to be confused with cultivar, a variety (abbreviated to var.) is a naturally-occurring difference from the standard species.  Its distinctiveness is not necessarily based on a geographic separation.

For example, Adromischus cristatus var. zeyheri is a variety of succulent plant that is distinct from the typical species as it lacks aerial roots and is a lime-green colour.

Forma

Like variety, forma (abbreviated to f.) is a naturally-occurring difference.  The differences at this level tend to be more minor than those which would be separated to variety.

For example, the species Veronica amplexicaulis has a distinct form with hairy leaves, Veronica amplexicaulis f. hirta.

Horticultural names

The term “variety” tends to be loosely applied in general conversation.  This broad usage of the word can lead to confusion!  Technically speaking:

Wild varieties are the product of evolution by natural selection.

Cultivars can be the product of artificial selection by human beings.

A cultivar is short for “cultivated variety”.  This is a plant selected by a grower for its desirable characteristics.  They must be distinct (with at least one unique characteristic), uniform (the distinguishing characteristics must be shared by all plants under the cultivar name) and stable (not reverting or changing characteristics).

Cultivars can arise in a number of different ways: some deliberate and some by chance!  They may come from an unusual individual found within a population of wild plants then brought into human cultivation, a sport (distinct growth from an existing plant), or a hybrid (crossbreeding of other plants).

Cultivar names

Historically, cultivar names were formatted in the same way as scientific names, with an adjoining term: e.g. Malus domestica cv. Granny Smith.  This method of formatting is no longer used.  To make cultivar names distinct from the rest of the plant name they are now always presented in single speech marks: e.g. Malus domestica ‘Granny Smith’.

Like botanical names, cultivar names have a variety of different origins.  They can be honorifics, given to celebrate or remember someone/something (including places), descriptive or fanciful.

• Rosa 'The Queen Elizabeth'
• Echeveria 'Perle von Nürnberg'
• Veronica 'Red Edge'
• Agave 'Purple People Eater'

There are no legal measures in place controlling the creation of new cultivar names.  The main way in which cultivar names are monitored is through the work of International Cultivar Registration Authorities (ICRAs).  ICRAs are generally administered by groups or individuals with a particular interest and knowledge of a genus, for example by plant societies and botanical gardens.  Some of our National Plant Collection holders serve as the ICRA for their genus, for example Tradescantia.

An ICRA is essentially a point of registration for a new cultivar within its given genus.  As the world of plants is vast, ICRAs do not exist for every single genus.  Therefore, the recording and consistency of names can vary markedly between genera with an ICRA and those without.

Trade designations and Plant Breeders' Rights (PBR)

Trade designations are selling names given to plants being released to horticultural markets, supplementary to their cultivar name.  These designations designed to be appealing and marketable, where the original cultivar names may not be.  Frequently, the cultivar names "behind" a trade designation are codes corresponding to the nurseries where the plants were created.  A trade designation should be written in distinct type (small capitals) with the cultivar name following in brackets so that they are not confused (although this may or may not be correctly conveyed on a plant's tags).

Unlike cultivar names, trade designations are not uniform: one plant might have several different trade designations, for example if it is sold in multiple countries.  For example, Rosa SURREY (‘Korlanum’)^PBR is sold in the UK, but the same rose is called Rosa SOMMERWIND (‘Korlanum’)^PBR in Germany and Rosa VENT D’ÉTÉ (‘Korlanum’)^PBR in France.

Plants with trade designations are often also covered by a form of intellectual property protection called Plant Breeders' Rights.  These rights prevent the use of this plant (propagation, sale or breeding) without the express permission of the breeder.  If a plant is subject to Plant Breeder's Rights, this should be also reflected in its name by the acronym ^PBR in superscript at the end of the name, as in the examples above.

In the USA, a similar system around intellectual property for plant breeders operates through the US Patent Office.

Series

Series are a way in which plants get subdivided below the level of genus.  The concept of a series tends to be more linked to horticultural practice, than botanical differences.  It is regularly used in marketing, where plants linked by a common theme are placed into a series: this often coincides with plants given Trade descriptions as mentioned above.

For example:

• The Pensham Series of Penstemon - all bred and introduced by Pershore Plant Raisers
• The Dalmatian Series of Digitalis, all selectively bred to flower in their first year (unlike most foxgloves)

These are written as Penstemon 'Pensham Princess' (Pensham Series)

Descriptors

Sometimes, we may encounter plants with additional information that helps to distinguish them, but that doesn't form part of the formal naming system.  The most common examples of this are variations in flower colour, distinct clones or regional variations of plants which haven't been allocated to separate infraspecific ranks.  Collector's numbers from wild-collected material are often added to the end of a plant name in this manner as well.

Descriptor type information follows on from the end of the formal name and is displayed in normal (non-italicised) text.

Examples:

• Amaryllis belladonna white-flowered
• Dionaea muscipula large clone
• Lithops dorotheae C124
• Sempervivum calcareum from Mont Ventoux, France