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Cultivated plant taxonomy
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Cultivated plant taxonomy is the study of the theory and practice of the science that finds, describes, classifies, identifies, and names cultigens – those plants whose origin or selection is primarily due to intentional human activity.
Cultivated plant taxonomy is one aspect of the study of horticultural botany mostly carried out in botanical gardens, large nurseries, universities or government departments.
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Encyclopedia
Cultivated plant taxonomy is the study of the theory and practice of the science that finds, describes, classifies, identifies, and names cultigens – those plants whose origin or selection is primarily due to intentional human activity.
Cultivated plant taxonomy is one aspect of the study of horticultural botany mostly carried out in botanical gardens, large nurseries, universities or government departments. Areas of interest to the professional horticultural taxonomist include: searching for new plants suitable for cultivation (plant hunting); communicating with and advising the general public on matters concerning the classification and nomenclature of cultivated plants and carrying out original research on these topics; describing the cultivated plants of particular regions (horticultural floras); recording new introductions; maintaining databases of cultivated plants; curating herbaria (including collections of dried specimens, images etc. ); developing collections of images; contributing to updates of the International Code of Nomenclature for Cultivated Plants (Cultivated Plant Code).
Scientific and anthropocentric classification
All classification systems serve a purpose. From the time of the ancient world, at least, we have classified plants according to two streams of thinking. On the one hand there is the detached academic, philosophical or scientific interest in plants themselves: then there is the practical, utilitarian or anthropocentric interest which emphasises the uses that we can make of them.
The following historical account of cultivated plant taxonomy illustrates the way these two approaches to plant nomenclature and classification have led to the present-day International Code of Botanical Nomenclature (Botanical Code) and International Code of Nomenclature for Cultivated Plants (Cultivated Plant Code).
The history of cultigen nomenclature has been discussed by William T. Stearn and Brandenberg, Hetterscheid and Berg. It has also been examined from a botanical perspective and for the period of separation of the two Codes from 1953 to 2004.
Nomenclature and classification
Biological nomenclature as expressed through the Botanical Code and Cultivated Plant Codes makes no assumptions as to the methods, principles or purposes of taxonomy, except that the units of taxonomy, the taxa, are placed in a nested hierarchy of ranks. In other words the Cultivated Plant Code of today is simply a mechanism for regulating those names in the classification categories cultivar and Group; it cannot make any further stipulations regarding the purpose or methods of taxonomy itself. Nevertheless, in dealing with the special classification categories needed for the plants of agriculture, horticulture and forestry the Cultivated Plant Code serves not only the scientific interests of formal nomenclature, it also caters for the special utilitarian needs of people dealing with the plants of commerce.
Historical development of cultivated plant taxonomy
The early development of cultigen taxonomy follows that of plant taxonomy in general as the early listing and documentation of plants made little distinction between those that were anthropogenic and those that were natural wild kinds. Formal plant nomenclature and classification would have evolved from the simple binomial system of folk taxonomy and it was not until the mid 19th century that the nomenclatural path of cultigens began to diverge from mainstream plant taxonomy.
10,000 to 400 BCE - plant domestication
William T. Stearn (1911-2001), renowned botanist, classical scholar and well-known author of the book Botanical Latin has commented that ”cultivated plants [cultigens] are mankind’s most vital and precious heritage from remote antiquity”.
Cultigens of our most common economic plants probably date back to the first settled communities of the Neolithic Revolution 10,000 to 12,000 years ago: their true origin will probably forever remain a mystery. In the Western world among the first cultigens would have been selections of the cereals wheat and barley that were made in the early settlements of the Fertile Crescent (the fertile river valleys of the Nile, Tigris and Euphrates) in the Western Mediterranean. However, food plant selections would also have arisen in the ten or so other centres of settlement that occurred around the world at this time. Confining crops to local areas gave rise to landraces (selections that are highly adapted to local conditions) although these are now largely replaced by modern cultivars. Cuttings are an extremely effective way of perpetuating desirable characters, especially of woody plants like grapes, figs and olives so it is not surprising that these constitute some of the first plants selections perpetuated in cultivation in the West. Migrating people would take their plant seeds and cuttings with them and there is some evidence of early Fertile Crescent cereal cultigens being transferred from Western Asia to surrounding lands.
400 BCE to 1400 - the ancient world: Greek and Roman influence and the Middle Ages
The more philosophical tradition is represented by Aristotle (384 BCE–322 BCE) who established the important idea of a fundamentum divisionis the principle that groups can be progressively divided. Biological classification of all organisms follows this principle of groups within groups which is known as a nested hierarchy. Although not necessarily based on the assumption of evolution, this form of classification fits well with the evolutionary pattern of descent with modification.
The early documentation of plants is attributed largely to Aristotle’s student Theophrastus (371-286 BCE). In his Enquiry into plants, he divided the plant kingdom primarily into trees, shrubs, undershrubs and herbs with further subdivision into wild and cultivated, flowering or not, deciduous or evergreen. Altogether he discussed about 480 kinds.
The utilitarian approach, dealing with plants mainly for their medicinal properties, is exemplified by the Roman nobleman, scientist and historian, Pliny the Elder (29-79 CE) author of Naturalis historiae , Pliny’s Natural History (which lists “cultivars” named after people, places and features of the cultivar), and Dioscorides (ca.40 - ca.90 CE) whose five volume Materia Medica was a forerunner of all modern pharmacopeias being one of the most influential herbals published between about 1470 and1670 CE: it listed 600 to 1000 different kinds of plants including Alba, Gallica, Centifolia and other roses grown by the Romans.
The first recorded naming of cultigens occurred in De Agri Cultura written about 160 BCE by Roman statesman Marcus Cato (234-149 BCE) in a list that includes 120 kinds (modern-day cultivars) of figs, grapes, apples and olives. The names are presented in a way that implies that they would have been familiar to fellow Romans. The “cultivar” names were mostly of one word and denoted the provenance of the cultivar (the geographical origin of the place where the plant selections were made).
Writers up to the fifteenth century added little to this early work. In the Middle Ages the Book of Hours, early herbals, illuminated manuscripts and economic records indicate that plants grown by the Romans found their way into monastery gardens. A poem written in AD 827 cited in refers to a monastery garden of St Gallen in Switzerland which cultivated sage, rue, southernwood, wormwood, horehound, fennel, German iris, lovage, salad, chervil, Madonna lily, opium poppy, clary, mint, betony, agrimony, catmint, radish, gallica rose, bottle gourd and melon. It seems likely that aromatic and culinary herbs were quite widespread and similar lists of plants occur in records of plants grown in Villa gardens at the time of Charlemagne (742-814 CE).
1400 to 1700 Renaissance, imperial expansion, herbals
The revival of learning during the Renaissance reinvigorated the study of plants and their classification.
From 1400 on, European expansion progressively established Latin as the common language of scholars in general and biological nomenclature in particular. The publication of herbals (books often illustrated with woodcuts describing the appearance, medicinal properties, and other characteristics of plants used in herbal medicine) from about 1500 extended the formal documentation of plants and by the late 1500s the number of different plant kinds documented had risen to about 4,000. In 1623 Caspar Bauhin published his Pinax theatre botanici an attempt at a comprehensive compilation of all plants known at that time: it included about 6000 kinds. The combined works of a German physician and botanist Valerius Cordus (1515-1544 CE) which were published in 1562 included many named “cultivars” including 30 apples and 49 pears, presumably local German selections.
With increasing trade in economic and medicinal plants the need for a more comprehensive system increased. Up to about 1650 plants had been grouped either alphabetically or according to utilitarian folk taxonomy - by their medicinal uses or whether they were trees, shrubs or herbs.
Between 1650 and 1700 there was a move from the utilitarian back to a scientific natural classification based on the characters of the plants themselves.
1700 to 1750 dawn of scientific classification
In 1700 French botanist J.P. de Tournefort (inspired by John Ray), although still using the broad groupings of “trees” and “herbs” for flowering plants, began to use flower characteristics as distinguishing features and, most importantly, provided a clear definition of the genus as a basic unit of classification. In Institutiones rei herbariae he listed about 10,000 different plants, which he called species, organised into 684 different genera. The establishment of this precursor of scientific classification vastly improved the organisation of plant variation into approximately equivalent groups or ranks and many of his genera were later taken up by Linnaeus. He is also attributed with the introduction of the word “herbarium” into general usage.
There was still at this time no agreement on the structure of a plant names so they ranged in length from one word to lengthy descriptive sentences. As the number of recorded plants increased so this system became more unwieldy as a means of communication about different plants.
1750-1800 Linnaeus and binomial nomenclature
European colonial expansion and the demand for description of thousands of new organisms highlighted difficulties with communication, the replication of descriptions and the importance of an agreed way of presenting, publishing and applying names.
It was the Swedish botanist Carl Linnaeus who finally put order into this situation through the publication of his Philosophia botanica (1736) and Critica botanica (1737). It was this work that formalised the name of a genus with a single epithet to form the name of a species as two words, the binomial. Linnaeus’ intention to list and classify the known biological world of his day began in 1753 with his Species Plantarum to be followed in 1758 by his Systema naturae which included animals.
In these works Linnaeus used a third name as a variety within a species and this was sometimes a “cultivated” variety, still written in Latin. Some of these Latin “cultigen” variety names have persisted to this day.
1800-1900 global plant trade
In England the tradition of documenting garden plants was established long before Linnaeus’ Species plantarum with the most prominent chronicler Philip Miller (1691-1771) who was in charge of the Chelsea Physic Garden in London from 1722 to 1770. He produced a voluminous publication on garden plants, The Gardeners Dictionary, the 1st edition in 1731 and the last and 8th edition in 1768 in which he finally adopted Linnaean binomials . For a while this was taken as the starting point for “horticultural” nomenclature equivalent to Linnaeus’ Species plantarum which is taken as the starting point for botanical nomenclature in general.
The natural distribution of plants across the world has determined when and where cultigens have been produced. The botanical and horticultural collection of economically important plants, including ornamentals, was based primarily on Europe. Although economic herbs and spices had a long history in trade, and there are good records of cultivar distribution by the Romans, botanical and horticultural exploration rapidly increased in the nineteenth century due to colonial expansion. New plants would have been brought back to Europe while, at the same time, valuable economic plants, including those from the tropics, would have been distributed among the colonies. This plant trade has provided the common global heritage of economic and ornamental cultigens that we use today and which formed the stock for modern plant selection, breeding, and genetic engineering.
The plant exchange that occurred as a result of European trade can be divided into several phases:
- to 1560 mostly within Europe
- 1560-1620 Near East (esp. bulbous plants from Turkey – “tulipomania”)
- 1620-1686 Canada and Virginia herbaceous plants
- 1687-1772 Cape of South Africa
- 1687-1772 North American trees and shrubs
- 1772-1820 Australia, Tasmania, New Zealand
- 1820-1900 Tropical glasshouse plants; hardy Japanese plants
- 1900-1930 West China
- 1930 Intensive breeding and selection programs
Botanical Code and cultigen nomenclature
As the community of people dealing with the cultigens of commerce grew so, once again, the divergence between taxonomy serving scientific purposes and utilitarian taxonomy meeting human needs re-emerged. In 1865 German botanist Karl Koch, who became General Secretary of the Berlin Horticultural Society, expressed resentment at the continued use of Latin for cultigen names. Many proposals to deal with this were made, perhaps the most prominent being the Lois de la nomenclature botanique submitted in 1867 to the fourth Horticultural and Botanical Congress by Swiss botanist Alphonse de Candolle who, in Article 40 stated:
“Seedlings, half-breeds (métis) of unknown origin or sports should receive from horticulturists fancy names (noms de fantaisie) in common language, as distinct as possible from the Latin names of species or varieties.”
This Article, making provision for the cultigens of horticultural nomenclature was to remain in the Botanical Code (with a minor amendment in 1935 suggesting the use of the letter ‘c’ before the horticultural name and antedating formal recognition of the cultivar) through 1906, 1912 and 1935 until the separation, in 1953, of the Horticultural Code, precursor to the International Code of Nomenclature for Cultivated Plants (Cultivated Plant Code).
In 1900 there was the first International Botanical Congress and in 1905 at the second Congress in Vienna an agreed set of nomenclatural rules was established, the Vienna Rules, which became known from then on as the International Code of Botanical Nomenclature. After World War II the responsibility for the Botanical Code was taken up by the International Association for Plant Taxonomy and meetings to discuss revisions are held at six-yearly intervals, the latest being in 2005
In horticulture at this time there existed all the problems that had confronted botanists in the nineteenth century - a plethora of names of various length, written and published in many languages with much duplication. The period between 1867 and 1953 was an uneasy time in which American horticulturists and other groups in Europe, such as the specialist orchid community, made attempts to put order into this chaos within their particular group of interest and devising their own rules for naming the plants of commerce.
Friedrich Alefeld (1820-1872), who used Latin variety names, in a monographic study of beans, lentils and other legumes distinguished three infraspecific taxonomic categories: Uterart (subspecies), Varietaten Gruppe and Kultur-Varietat, all with Latin names. In doing this he was probably laying the ground for the later establishment of the cultigen classification categories cultivar and Group. In conjunction with the Brussels International Botanical Congress of 1910 there was an International Horticultural Congress having a horticultural nomenclature component.
As a result of general dissatisfaction and a submission from the Royal Horticultural Society London the Règles de Nomenclature Horticole was established
The use of simple descriptive Latin names (e.g. compactus, nanus, prostratus) for horticultural variants was accepted and so too were names in the local language – which were not to be translated and should preferably consist of one word and a maximum of three. This first “Horticultural Code” consisted of 16 Articles. However, with the intercession of a World War I it was not until the 9th Horticultural Congress in London in 1930 that the rules of a Horticuture Nomenclature Committee were agreed and added as an Appendix to the 1935 Botanical Code. The rules established in 1935 were accepted but needed to be extended to include the cultigens of agriculture and forestry, but it was only a result of discussions at the 1950 International Botanical Congress in Stockholm and the 18th International Horticultural Congress in London in 1952 the first International Code of Nomenclature for Cultivated Plants was published in 1953. The American horticultural botanist Liberty Hyde Bailey was responsible for coining the word cultigen in 1918
and cultivar in 1923 but these are only two accepted terms in a multitude of unused classification terms and categories suggested to designate cultigens
International Code of Nomenclature for Cultivated Plants
The first Cultivated Plant Code (Wageningen), which was published in 1953, has been followed by seven subsequent editions - in 1958 (Utrecht), 1961 (update of 1958), 1969 (Edinburgh), 1980 (Seattle), 1995 (Edinburgh), and 2004 (Toronto).
Following the structure of the Botanical Code the Cultivated Plant Code is set out in the form of an initial set of Principles followed by Rules and Recommendations that are subdivided into Articles. Amendments to the Cultivated Plant Code are prompted by international symposia for cultivated plant taxonomy which allow for rulings made by the International Commission on the Nomenclature of Cultivated Plants. Each new Cultivated Plant Code includes a summary of the changes made to the previous version and these have also been summarised for the period 1953 to 1995.
International Association for Cultivated Plant Taxonomy
Over the last 15 or so years there has been concern about international communication on cultivated plant taxonomy, organisation of international symposia, and general communication on topics of interest. In 1988 a Horticultural Taxonomy Group (Hortax) was formed in the UK and a parallel organisation, the Nomenclature and Registration Working Group of the Vaste Keurings Commissie in the Netherlands. One development promoting discussion was the newsletter Hortax News which was superseded in February 2006 by the first issue of Hanburyana, a journal produced by the Royal Horticultural Society in London and dedicated to horticultural taxonomy. This filled a gap left when the American journal Baileya ceased publication in the early 1990s. Another development was the launch, in 2007, at the Sixth Symposium on the Taxonomy of Cultivated Plants at Wageningen of the International Association for Cultivated Plant Taxonomy.
Contemporary cultigen nomenclature
Most cultigens have names consisting of a Latin name that is governed by the International Code of Botanical Nomenclature e.g. Malus domestica, to which is added a cultigen epithet, enclosed in single quotes e.g. Malus domestica ‘Granny Smith’. There are two classification categories (ranks) used for cultigens – the cultivar and the Group and the formation and use of these names is regulated by the ICNCP. Examples of acceptable ways to present cultigen names are given below:
Prunus serrata Sato-zakura Group
Prunus serrata (Sato-zakura Group) ‘Ojochin’
Prunus ‘Ojochin’
Flowering cherry ‘Ojochin’
See also
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