Cultivar

In agricultural science, a cultivar is a cultivated selection that can be propagated reliably in a prescribed manner. This may be by seed, by grafting or it may be vegetatively propagated, i.e, be a clone. The word cultivar is a portmanteau coined from "cultivated" and "variety". Cultivars may be either particularly desirable selections from populations of a single species, or hybrids between species. Sometimes a cultivar can be placed within a species, but this is not required; in popular genera (such as Dahlia, Hosta or Rosa) the breeding lines are so complex that it would be impossible to ascribe most cultivars to any particular species. In some plant families, e.g. Orchidaceae, multi-generic crosses are common.

Cultivar names

Cultivars are identified by uniquely distinguishing names. Names of cultivars are regulated by the International Code of Nomenclature for Cultivated Plants (ICNCP, commonly known as the "Cultivated Plant Code") and registered with an International Cultivar Registration Authority and conform to the rules of the ISHS (International Society for Horticultural Science) Commission for Nomenclature and Cultivar Registration. There are separate authorities for different plant-groups. In addition, cultivars may get a trademark name, protected by law (see Trade Designations and "Selling Names", below).

A cultivar name consists of a botanical name (of a genus, species, infraspecific taxon, interspecific hybrid or intergeneric hybrid) followed by a cultivar epithet. The cultivar epithet is capitalised and put between single quotes: preferably it should not be italicized. Cultivar epithets published before 1 January 1959 were often given a Latin form and can be readily confused with the specific epithets in botanical names: after that date, new cultivar epithets must be in a modern vernacular language to distinguish them from botanical epithets.

Cryptomeria japonica 'Elegans'

Chamaecyparis lawsoniana 'Aureomarginata' (pre-1959 name, Latin in form)

Chamaecyparis lawsoniana 'Golden Wonder' (post-1959 name, English language)

Pinus densiflora 'Akebono' (post-1959 name, Japanese language)

Some incorrect examples:

Cryptomeria japonica "Elegans" (double quotes are unacceptable)

Berberis thunbergii cv. 'Crimson Pygmy' (this once-common usage is now unacceptable, as it is no longer correct to use "cv." in this context; Berberis thunbergii 'Crimson Pygmy' is correct)

Rosa cv. 'Peace' (this is now incorrect for two reasons: firstly, the use of "cv."; secondly, "Peace" is a trade designation or "selling name" for the cultivar R. 'Madame A. Meilland' and should therefore be printed in a different typeface from the rest of the name, without any quote marks, for example: Rosa Peace.)

Where several very similar cultivars exist, these are termed Cultivar Groups; the name is in normal type and capitalised as in a single cultivar, but not in single quotes, and followed by "Group" (or its equivalent in other languages)

Brassica oleracea Capitata Group (the group of cultivars including all typical cabbages)

Brassica oleracea Botrytis Group (the group of cultivars including all typical cauliflowers)

Hydrangea macrophylla Groupe Hortensis (in French) = Hydrangea macrophylla Hortensia Group (in English)

Where cited with a cultivar name the Cultivar Group should be enclosed in parentheses, as follows:

Hydrangea macrophylla (Hortensia Group) 'Ayesha'

Some cultivars and Cultivar Groups are so well 'fixed' or established that they 'come true from seed', meaning that the plants from a seed sowing (rather than vegetatively propagated) will show very little variation. In the past, such plants were often called by the terms 'variety', 'selection' or 'strain'; these terms (particularly variety, which has a very different botanical meaning) are best avoided with cultivated plants. Normally, however, plants grown from seed taken from a cultivar can be very variable and such seeds or seedling plants should never be labelled with, or sold under, the parent cultivar's name (See [1] an article by Tony Lord of The RHS Plant Finder).

Trade Designations and "Selling Names"

Cultivars that are still being developed and not yet ready for release to retail sale are often coded with letters and/or numbers before being assigned a name. It is common for this code name to be quoted alongside the new cultivar name or trade designation when the plant is made available commercially (for example Rosa Fascination = 'Poulmax') and this may continue, in books or magazines and on plant labels, for several years after the plant was released. Because a name that is attractive in one language may have less appeal in another country, a plant may be given different selling names from country to country. Quoting the code allows the correct identification of cultivars around the world and helps to avoid the once-common situation where the same plant might, confusingly, be sold under several different names in one country, having been imported under different aliases.

Another form of what the Cultivated Plant Code calls a trade designation is the plant "variety", as defined in the UPOV Convention. Not to be confused with the botanical rank of variety.

Cultivars in the natural world

Many cultivars are "naturalized" in gardening, in other words they are planted out and largely left to their own devices. With pollination and regrowth from seed, true natural processes, the distinct cultivars will disappear over time. The cultivar's genetic material however may become part of the gene pool of a population, where it will be largely but not completely swamped. Cultivars that have originated as hybrids of different species are exotic, as is a plant from a different continent, or even a different part of the same country. They are a threat to the true type of a species, and should never be planted out in the wild, or where they are likely to cross-pollinate with their wild relatives.

Legal points

With plants produced by genetic engineering becoming more and more widely used, it is important to note that the companies producing these plants (or plants produced by traditional means) often claim a patent on their product. Thus the notion that "letting seed germinate and grow into a crop is the most natural thing in the world" is no longer appropriate; it can be illegal to harvest seeds (even in one's own fields) from a patented " variety" (which may or may not also be a cultivar) except for personal use. Such plants are often labelled "PBR", which stands for " plant breeders' rights", or "PVR", which stands for "plant variety rights").

The practice of patenting living plants is often considered unethical, especially where a "variety" has simply been selected from a wild population or is a chance sport among cultivated plants. However, where the "variety" is the result of a deliberate breeding programme by a nurseryman or plant breeder it may be the result of years of dedicated work involving painstaking trialling and selection. The patent (which is itself expensive to obtain) is thought to protect the breeder's right to obtain some financial reward for their work, normally for a limited period and geographical area.