A cultivar[nb 1] (cultivated variety) is an assemblage of plants selected for desirable characteristics that are maintained during propagation. More generally, a cultivar is the most basic classification category of cultivated plants in the International Code of Nomenclature for Cultivated Plants (ICNCP). Most cultivars arose in cultivation, but a few are special selections from the wild.
Popular ornamental garden plants like roses, camellias, daffodils, rhododendrons, and azaleas are cultivars produced by careful breeding and selection for floral colour and form. Similarly, the world's agricultural food crops are almost exclusively cultivars that have been selected for characters such as improved yield, flavour, and resistance to disease, and very few wild plants are now used as food sources. Trees used in forestry are also special selections grown for their enhanced quality and yield of timber.
Cultivars form a major part of Liberty Hyde Bailey's broader group, the cultigen, which is defined as a plant whose origin or selection is primarily due to intentional human activity. A cultivar is not the same as a botanical variety, which is a taxonomic rank below subspecies, and there are differences in the rules for creating and using the names of botanical varieties and cultivars. In recent times, the naming of cultivars has been complicated by the use of statutory patents for plants and recognition of plant breeders' rights.
The International Union for the Protection of New Varieties of Plants (UPOV – French: Union internationale pour la protection des obtentions végétales) offers legal protection of plant cultivars to persons or organisations that introduce new cultivars to commerce. UPOV requires that a cultivar be "distinct, uniform", and "stable". To be "distinct", it must have characters that easily distinguish it from any other known cultivar. To be "uniform" and "stable", the cultivar must retain these characters in repeated propagation.
The naming of cultivars is an important aspect of cultivated plant taxonomy, and the correct naming of a cultivar is prescribed by the Rules and Recommendations of the International Code of Nomenclature for Cultivated Plants (ICNCP, commonly denominated the Cultivated Plant Code). A cultivar is given a cultivar name, which consists of the scientific Latin botanical name followed by a cultivar epithet. The cultivar epithet is usually in a vernacular language. For example, the full cultivar name of the King Edward potato is Solanum tuberosum 'King Edward'. 'King Edward' is the cultivar epithet, which, according to the Rules of the Cultivated Plant Code, is bounded by single quotation marks.
The word cultivar originated from the need to distinguish between wild plants and those with characteristics that arose in cultivation, presently denominated cultigens. This distinction dates to the Greek philosopher Theophrastus (370–285 BC), the "Father of Botany", who was keenly aware of this difference. Botanical historian Alan Morton noted that Theophrastus in his Historia Plantarum (Enquiry into Plants) "had an inkling of the limits of culturally induced (phenotypic) changes and of the importance of genetic constitution" (Historia Plantarum, Book 3, 2, 2 and Causa Plantarum, Book 1, 9, 3).
The International Code of Nomenclature for algae, fungi, and plants uses as its starting point for modern botanical nomenclature the Latin names in Linnaeus' (1707–1778) Species Plantarum (tenth edition) and Genera Plantarum (fifth edition). In Species Plantarum, Linnaeus enumerated all plants known to him, either directly or from his extensive reading. He recognised the rank of varietas (botanical "variety", a rank below that of species and subspecies) and he indicated these varieties with letters of the Greek alphabet, such as α, β, and λ, before the varietal name, rather than using the abbreviation "var." as is the present convention. Most of the varieties that Linnaeus enumerated were of "garden" origin rather than being wild plants.
In time the need to distinguish between wild plants and those with variations that had been cultivated increased. In the nineteenth century many "garden-derived" plants were given horticultural names, sometimes in Latin and sometimes in a vernacular language. From circa the 1900s, cultivated plants in Europe were recognised in the Scandinavian, Germanic, and Slavic literature as stamm or sorte, but these words could not be used internationally because, by international agreement, any new denominations had to be in Latin. In the twentieth century an improved international nomenclature was proposed for cultivated plants.
The cultigen is a species, or its equivalent, that has appeared under domestication – the plant is cultigenous. I now propose another name, cultivar, for a botanical variety, or for a race subordinate to species, that has originated under cultivation; it is not necessarily, however, referable to a recognized botanical species. It is essentially the equivalent of the botanical variety except in respect to its origin.
In that essay, Bailey used only the rank of species for the cultigen, but it was obvious to him that many domesticated plants were more like botanical varieties than species, and that realization appears to have motivated the suggestion of the new category of cultivar.
Bailey created the word cultivar, which is generally assumed to be a portmanteau of cultivated and variety. Bailey never explicitly stated the etymology of cultivar, and it has been suggested that it is instead a contraction of cultigen and variety, which seems correct. The neologism cultivar was promoted as "euphonious" and "free from ambiguity".[nb 2] The first Cultivated Plant Code of 1953 subsequently commended its use, and by 1960 it had achieved common international acceptance.
The words cultigen and cultivar may be confused with each other. A cultigen is any plant that is deliberately selected for or altered in cultivation, as opposed to an indigen; the Cultivated Plant Code states that cultigens are "maintained as recognisable entities solely by continued propagation". Cultigens can have names at any of many taxonomic ranks, including those of grex, species, cultivar group, variety, form, and cultivar; and they may be plants that have been altered in cultivation, including by genetic modification, but have not been formally denominated. A cultigen or a component of a cultigen can be accepted as a cultivar if it is recognisable and has stable characters. Therefore, all cultivars are cultigens, because they originate in cultivation, but not all cultigens are cultivars, because some cultigens have not been formally distinguished and denominated as cultivars.
The Cultivated Plant Code notes that the word cultivar is used in two different senses: first, as a "classification category" the cultivar is defined in Article 2 of the International Code of Nomenclature for Cultivated Plants (2009, 8th edition) as follows: The basic category of cultivated plants whose nomenclature is governed by this Code is the cultivar. There are two other classification categories for cultigens, the grex and the group. The Code then defines a cultivar as a "taxonomic unit within the classification category of cultivar". This is the sense of cultivar that is most generally understood and which is used as a general definition.
A cultivar is an assemblage of plants that (a) has been selected for a particular character or combination of characters, (b) is distinct, uniform and stable in those characters, and (c) when propagated by appropriate means, retains those characters.
Members of a particular cultivar are not necessarily genetically identical. The Cultivated Plant Code emphasizes that different cultivated plants may be accepted as different cultivars, even if they have the same genome, while cultivated plants with different genomes may be regarded as the same cultivar. The production of cultivars generally entails considerable human involvement although in a few cases it may be as little as simply selecting variation from plants growing in the wild (whether by collecting growing tissue to propagate from or by gathering seed).
Cultivars generally occur as ornamentals and food crops: Malus 'Granny Smith' and Malus 'Red Delicious' are cultivars of apples propagated by cuttings or grafting, Lactuca 'Red Sails' and Lactuca 'Great Lakes' are lettuce cultivars propagated by seeds. Named cultivars of Hosta and Hemerocallis plants are cultivars produced by micropropagation or division.
Cultivars that are produced asexually are genetically identical and known as clones; this includes plants propagated by division, layering, cuttings, grafts, and budding. The propagating material may be taken from a particular part of the plant, such as a lateral branch, or from a particular phase of the life cycle, such as a juvenile leaf, or from aberrant growth as occurs with witch's broom. Plants whose distinctive characters are derived from the presence of an intracellular organism may also form a cultivar provided the characters are reproduced reliably from generation to generation. Plants of the same chimera (which have mutant tissues close to normal tissue) or graft-chimeras (which have vegetative tissue from different kinds of plants and which originate by grafting) may also constitute a cultivar.
Some cultivars "come true from seed", retaining their distinguishing characteristics when grown from seed. Such plants are termed a "variety", "selection" or "strain" but these are ambiguous and confusing words that are best avoided. In general, asexually propagated cultivars grown from seeds produce highly variable seedling plants, and should not be labelled with, or sold under, the parent cultivar's name.
Seed-raised cultivars may be produced by uncontrolled pollination when characteristics that are distinct, uniform and stable are passed from parents to progeny. Some are produced as "lines" that are produced by repeated self-fertilization or inbreeding or "multilines" that are made up of several closely related lines. Sometimes they are F1 hybrids which are the result of a deliberate repeatable single cross between two pure lines. A few F2 hybrid seed cultivars also exist, such as Achillea 'Summer Berries'.
Some cultivars are agamospermous plants, which retain their genetic composition and characteristics under reproduction. Occasionally cultivars are raised from seed of a specially selected provenance – for example the seed may be taken from plants that are resistant to a particular disease.
Genetically modified plants with characteristics resulting from the deliberate implantation of genetic material from a different germplasm may form a cultivar. However, the International Code of Nomenclature for Cultivated Plants notes, "In practice such an assemblage is often marketed from one or more lines or multilines that have been genetically modified. These lines or multilines often remain in a constant state of development which makes the naming of such an assemblage as a cultivar a futile exercise."  However, retired transgenic varieties such as the Fish tomato, which are no longer being developed, do not run into this obstacle and can be given a cultivar name.
Cultivars may be selected because of a change in the ploidy level of a plant which may produce more desirable characteristics.
Every unique cultivar has a unique name within its denomination class (which is almost always the genus). Names of cultivars are regulated by the International Code of Nomenclature for Cultivated Plants, and may be registered with an International Cultivar Registration Authority (ICRA). There are sometimes separate registration authorities for different plant types such as roses and camellias. In addition, cultivars may be associated with commercial marketing names referred to in the Cultivated Plant Code as "trade designations" (see 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 enclosed by single quotes; it should not be italicized if the botanical name is italicized; and each of the words within the epithet is capitalized (with some permitted exceptions such as conjunctions). It is permissible to place a cultivar epithet after a common name provided the common name is botanically unambiguous. 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, newly coined cultivar epithets must be in a modern vernacular language to distinguish them from botanical epithets.
Where several very similar cultivars exist they can be associated into a Group (formerly Cultivar-group). As Group names are used with cultivar names it is necessary to understand their way of presentation. Group names are presented in normal type and the first letter of each word capitalised as for cultivars, but they are not placed in single quotes. When used in a name, the first letter of the word "Group" is itself capitalized.
Since the 1990s there has been an increasing use of legal protection for newly produced cultivars. Plant breeders expect legal protection for the cultivars they produce. According to proponents of such protections, if other growers can immediately propagate and sell these cultivars as soon as they come on the market, the breeder's benefit is largely lost. Legal protection for cultivars is obtained through the use of Plant breeders’ rights and plant Patents but the specific legislation and procedures needed to take advantage of this protection vary from country to country.
The use of legal protection for cultivars can be controversial, particularly for food crops that are staples in developing countries, or for plants selected from the wild and propagated for sale without any additional breeding work; some people consider this practice unethical.
The formal scientific name of a cultivar, like Solanum tuberosum ‘King Edward’, is a way of uniquely designating a particular kind of plant. This scientific name is in the public domain and cannot be legally protected. Plant retailers wish to maximize their share of the market and one way of doing this is to replace the cumbersome Latin scientific names on plant labels in retail outlets with appealing marketing names that are easy to use, pronounce, and remember. Marketing names lie outside the scope of the Cultivated Plant Code which refers to them as "trade designations". If a retailer or wholesaler has the sole legal rights to a marketing name then that may offer a sales advantage. Plants protected by plant breeders' rights (PBR) may have a "true" cultivar name – the recognized scientific name in the public domain – and a "commercial synonym" – an additional marketing name that is legally protected. An example would be Rosa Fascination = 'Poulmax', in which Rosa is the genus, Fascination is the trade designation, and ‘Poulmax’ is scientific cultivar name.
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 original cultivar name allows the correct identification of cultivars around the world.
The main body coordinating plant breeders' rights is the International Union for the Protection of New Varieties of Plants (Union internationale pour la protection des obtentions végétales, UPOV) and this organization maintains a database of new cultivars protected by PBR in all countries.
An International Cultivar Registration Authority (ICRA) is a voluntary, non-statutory organization appointed by the Commission for Nomenclature and Cultivar Registration of the International Society of Horticultural Science. ICRAs are generally formed by societies and institutions specializing in particular plant genera such as Dahlia or Rhododendron and are currently located in Europe, North America, China, India, Singapore, Australia, New Zealand, South Africa and Puerto Rico.
Each ICRA produces an annual report and its reappointment is considered every four years. The main task is to maintain a register of the names within the group of interest and where possible this is published and placed in the public domain. One major aim is to prevent the duplication of cultivar and Group epithets within a genus, as well as ensuring that names are in accord with the latest edition of the Cultivated Plant Code. In this way, over the last 50 years or so, ICRAs have contributed to the stability of cultivated plant nomenclature. In recent times many ICRAs have also recorded trade designations and trademarks used in labelling plant material, to avoid confusion with established names.
New names and other relevant data are collected by and submitted to the ICRA and in most cases there is no cost. The ICRA then checks each new epithet to ensure that it has not been used before and that it conforms with the Cultivated Plant Code. Each ICRA also ensures that new names are formally established (i.e. published in hard copy, with a description in a dated publication). They record details about the plant, such as parentage, the names of those concerned with its development and introduction, and a basic description highlighting its distinctive characters. ICRAs are not responsible for assessing the distinctiveness of the plant in question. Most ICRAs can be contacted electronically and many maintain web sites for an up-to-date listing.
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.Broccoli
Broccoli is an edible green plant in the cabbage family (family Brassicaceae, genus Brassica) whose large flowering head and stalk is eaten as a vegetable. The word broccoli comes from the Italian plural of broccolo, which means "the flowering crest of a cabbage", and is the diminutive form of brocco, meaning "small nail" or "sprout".Broccoli is classified in the Italica cultivar group of the species Brassica oleracea. Broccoli has large flower heads, usually dark green in color, arranged in a tree-like structure branching out from a thick, edible stalk which is usually light green. The mass of flower heads is surrounded by leaves. Broccoli resembles cauliflower, which is a different cultivar group of the same Brassica species. Combined in 2017, China and India produced 73% of the world's broccoli and cauliflower crops.Broccoli resulted from breeding of cultivated Brassica crops in the northern Mediterranean starting in about the sixth century BC. Since the time of the Roman Empire, broccoli has been commonly consumed, and is eaten raw or cooked. Broccoli is a particularly rich source of vitamin C and vitamin K. Contents of its characteristic sulfur-containing glucosinolate compounds, isothiocyanates and sulforaphane, are diminished by boiling, but are better preserved by steaming, microwaving or stir-frying.Rapini, sometimes called "broccoli raab" among other names, forms similar but smaller heads, and is actually a type of turnip (Brassica rapa).Cultivar group
A Group (previously cultivar-group) is a formal category in the International Code of Nomenclature for Cultivated Plants (ICNCP) used for cultivated plants (cultivars) that share a defined characteristic. It is represented in a botanical name by the symbol Group or Gp. "Group" or "Gp" is always written with a capital G in a botanical name, or epithet. The Group is not italicized in a plant's name. The ICNCP introduced the term and symbol "Group" in 2004, as a replacement for the lengthy and hyphenated "cultivar-group", which had previously been the category's name since 1969. For the old name "cultivar-group", the non-standard abbreviation cv. group or cv. Group is also sometimes encountered. There is a slight difference in meaning, since a cultivar-group was defined to comprise cultivars, whereas a Group may include individual plants.The ICNCP distinguishes between the terms "group" and "Group", a "group" being "an informal taxon not recognized in the ICBN", while a "Group" is the formal taxon defined by the ICNCP (see above).This categorization does not apply to plant taxonomy generally, only to horticultural and agricultural contexts. Any given Group may have a different taxonomic classification, such as a subspecific name (typically a form or variety name, given in italics) after the genus and species.
A Group is usually united by a distinct common trait, and often includes members of more than one species within a genus. For example, early flowering cultivars in the genus Iris form the Iris Dutch Group. A plant species that loses its taxonomic status in botany, but still has agricultural or horticultural value, meets the criteria for a cultivar group, and its former botanical name can be reused as the name of its cultivar group. For example, Hosta fortunei is usually no longer recognized as a species, and the ICNCP states that the epithet fortunei can be used to form Hosta Fortunei Group.Helianthus
Helianthus or sunflower () is a genus of plants comprising about 70 species. Except for three species in South America, all Helianthus species are native to North America and Central America. The common name, "sunflower", typically refers to the popular annual species Helianthus annuus, or the common sunflower, whose round flower heads in combination with the ligules look like the sun. This and other species, notably Jerusalem artichoke (H. tuberosus), are cultivated in temperate regions and some tropical regions as food crops for humans, cattle, and poultry, and as ornamental plants. The species H. annuus typically grows during the summer and into early fall, with the peak growth season being mid-summer.Perennial sunflower species are not as common in garden use due to their tendency to spread rapidly and become invasive. The whorled sunflower, Helianthus verticillatus, was listed as an endangered species in 2014 when the U.S. Fish and Wildlife Service issued a final rule protecting it under the Endangered Species Act. The primary threats are industrial forestry and pine plantations in Alabama, Georgia, and Tennessee. They grow to 1.8 m (6 ft) and are primarily found in woodlands, adjacent to creeks and moist, prairie-like areas.Ulmus 'Alata'
This cultivar should not be confused with the American species Ulmus alata, commonly known as the 'Winged Elm'.The elm cultivar Ulmus 'Alata' was first mentioned by Kirchner, in Petzold & Kirchner, Arboretum Muscaviense 566, 1864, as Ulmus montana (: glabra) alata, but without description.Ulmus 'Folia Aurea'
The elm cultivar Ulmus 'Folia Aurea' was first identified (as U. campestris var. foliis aureis) by Loudon in Arboretum et Fruticetum Britannicum, 3: 1378, 1838.Ulmus 'Hertfordensis Angustifolia'
The elm cultivar Ulmus 'Hertfordensis Angustifolia' was mentioned (as Ulmus campestris hertfordensis angustifolia) by Boulger in Gardener's Chronicle II. 12: 298 1879, but without description.Ulmus 'Nigrescens'
The elm cultivar Ulmus 'Nigrescens' was identified by Pynaert  as Ulmus campestris betulaefolia nigrescens. Considered by Green to be "probably Ulmus carpinifolia (: minor), but said to have been raised from seed of Purpurea".Ulmus americana 'Aurea'
The American Elm cultivar Ulmus americana 'Aurea' was cloned from a tree discovered by F. L. Temple in Vermont at the end of the 19th century.Ulmus americana 'Minneapolis Park'
The American Elm cultivar Ulmus americana 'Minneapolis Park' was a selection made by the Minneapolis Park Department as being particularly suited to boulevard planting.Ulmus americana 'Nigricans'
The American Elm cultivar Ulmus americana 'Nigricans' was cloned from a selection made from seedlings raised by the Zöschener Baumschule, Germany, at the end of the 19th century.Ulmus americana 'Queen City'
The American Elm cultivar Ulmus americana 'Queen City' was a selection made c. 1944 from a tree growing on the Lake Shore Boulevard in Toronto, Ontario, Canada.Ulmus americana 'Vase'
The putative American Elm cultivar Ulmus americana 'Vase' was listed in Edition 5 of the 1949 Plant Buyers Guide. No details of provenance are available, and its status as a true cultivar is uncertain. Green regarded the tree as "..neither clonal nor a true cultivar". The tree features in the Plumfield Nurseries wholesale trade list of 1931, but without description or provenance.Ulmus glabra 'Minor'
The Wych Elm cultivar Ulmus glabra 'Minor' was described by Loudon in Arboretum et Fruticetum Britannicum 3: 1398, 1838.Ulmus minor 'Argenteo-Variegata'
The Field Elm cultivar Ulmus minor 'Argenteo-Variegata' or simply 'Variegata', known in Australasia and North America as Silver Elm or Tartan Elm, is said to have been cultivated in France from 1772. Green noted that variegated forms of Field Elm "arise frequently, and several clones may have been known under this name". Dumont de Courset (1802) listed an U. campestris var. glabra variegata, Loudon (1838) an U. nitens var. variegata, and Wesmael (1863) an U. campestris var. nuda microphylla variegata.'Variegata' is not to be confused with the variegated English Elm cultivar, U. minor 'Atinia Variegata', which has the broader, almost orbicular leaves of the type.Ulmus minor 'Atinia Pyramidalis'
The Field Elm cultivar Ulmus minor 'Atinia Pyramidalis', was first described as U. campestris pyramidalis by Vicary Gibbs in the Gardeners' Chronicle (1922). 'Pyramidalis' reportedly originated from a bud sport of "common elm" (English Elm) at Gibbs' Aldenham estate, Hertfordshire, England, c. 1890.Not to be confused with the cultivar known as pyramidalm [:pyramid elm] in Scandinavia, which is trimmed Exeter Elm.Ulmus minor 'Atinia Variegata'
The Field Elm cultivar Ulmus minor 'Atinia Variegata', the Variegated-leaved common English Elm, formerly known as U. procera 'Argenteo-Variegata' and described by Weston (1770) as U. campestris argenteo-variegata, is believed to have originated in England in the seventeenth century and to have been cultivated since the eighteenth. The Oxford botanist Robert Plot mentioned in a 1677 Flora a variegated elm in Dorset, where English Elm is the common field elm. Elwes and Henry (1913) had no doubt that the cultivar was of English origin, "as it agrees with the English Elm in all its essential characters". At the Dominion Arboretum, Ottawa, the tree was listed as U. procera 'Marginata', as the variegation is sometimes most obvious on leaf-margins.Variegated English elm is not to be confused with the more common Field Elm cultivar U. minor 'Argenteo-Variegata', also known as U. minor 'Variegata', the Silver Elm or Tartan Elm, which has similar markings but narrower leaves.Ulmus minor 'Laciniata'
The Field Elm cultivar Ulmus minor 'Laciniata' was listed by Wesmael  in Bulletin de la Fédération des sociétés d'horticulture de Belgique 1862: 390 1863 as Ulmus campestris var. nuda subvar. microphylla laciniata Hort. Vilv..Ulmus minor 'Purpurea'
The Purple-leafed Jersey or Guernsey Elm Ulmus minor 'Purpurea' is largely confined to Australia.
Breeds and cultivars
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