Cultivated plant taxonomy
Cultivated plant taxonomy is the study of the theory and practice of the science that identifies, describes, classifies, and names cultigens—those plants whose origin or selection is primarily due to intentional human activity. Cultivated plant taxonomists do, however, work with all kinds of plants in cultivation.
Cultivated plant taxonomy is one part of the study of horticultural botany which is mostly carried out in botanical gardens, large nurseries, universities, or government departments. Areas of special interest for the cultivated plant taxonomist include: searching for and recording new plants suitable for cultivation ; 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 ; maintaining databases, herbaria and other information about cultivated plants.
Much of the work of the cultivated plant taxonomist is concerned with the naming of plants as prescribed by two plant nomenclatural Codes. The provisions of the International Code of Nomenclature for algae, fungi, and plants serve primarily scientific ends and the objectives of the scientific community, while those of the International Code of Nomenclature for Cultivated Plants are designed to serve both scientific and utilitarian ends by making provision for the names of plants used in commerce—the cultigens that have arisen in agriculture, forestry and horticulture. These names, sometimes called variety names, are not in Latin but are added onto the scientific Latin names, and they assist communication among the community of foresters, farmers and horticulturists.
The history of cultivated plant taxonomy can be traced from the first plant selections that occurred during the agrarian Neolithic Revolution to the first recorded naming of human plant selections by the Romans. The naming and classification of cultigens followed a similar path to that of all plants until the establishment of the first Cultivated Plant Code in 1953 which formally established the cultigen classification category of cultivar. Since that time the classification and naming of cultigens has followed its own path.
Distinctive characteristics
Cultivated plant taxonomy has been distinguished from the taxonomy of other plants in at least five ways.- Firstly, there is a distinction made according to where the plants are growing — that is, whether they are wild or cultivated. This is alluded to by the Cultivated Plant Code which specifies in its title that it is dealing with cultivated plants.
- Secondly, a distinction is made according to how the plants originated. This is indicated in Principle 2 of the Cultivated Plant Code which defines the scope of the Code as "... plants whose origin or selection is primarily due to the intentional actions of mankind" — plants that have evolved under natural selection with human assistance.
- Thirdly, cultivated plant taxonomy is concerned with plant variation that requires the use of special classification categories that do not conform with the hierarchy of ranks implicit in the Botanical Code, these categories being the cultivar, Group and grex. This feature is also referred to in the Preamble to the Cultivated Plant Code which states that "The purpose of giving a name to a taxon is not to indicate its characters or history, but to supply a means of referring to it and to indicate to which category it is assigned."
- Fourthly, cultivated plant taxonomy serves a particular community of people: the Botanical Code focuses on the needs of plant taxonomists as they attempt to maintain order and stability for the scientific names of all plants, while the Cultivated Plant Code caters for the needs of people requiring names for plants used in the commercial world of agriculture, forestry and horticulture.
- Finally, the difference between cultivated plant taxonomy and the taxonomy of other plants has been attributed to the purpose for which the taxonomy has been devised, it being plant-centred in the Botanical Code and human-centred in the Cultivated Plant Code.
Scientific and anthropocentric classification
From the time of the ancient world, at least, plants have been classified in two ways. On the one hand there is the detached academic, philosophical or scientific interest in plants themselves: this groups plants by their relationship to one another according to their similarities and differences in structure and function. Then there is the practical, utilitarian or anthropocentric interest which groups plants according to their human use. Cultivated plant taxonomy is concerned with the special classification categories needed for the plants of agriculture, horticulture and forestry as regulated by the Cultivated Plant Code. This 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. Those cultigens given names governed by the Cultivated Plant Code fulfill three criteria: they have special features considered of sufficient importance to warrant a name; the special features are the result of deliberate human breeding or selection and are not found in wild populations ; it is possible to perpetuate the desirable features by propagation in cultivation.
The terms cultigen and cultivar may be confused with each other. Cultigen is a general-purpose term for plants that have been deliberately altered or specially selected by humans, while cultivar is a formal classification category. Cultigens include not only plants with cultivar names but also those with names in the classification categories of grex and Group. The Cultivated Plant Code points out that cultigens are: deliberately selected plants that may have arisen by intentional or accidental hybridization in cultivation, by selection from existing cultivated stocks, or from variants within wild populations that are maintained as recognizable entities solely by continued propagation. Included within the group of plants known as cultigens are genetically modified plants, plants with binomial Latin names that are the result of ancient human selection, and any plants that have been altered by humans but which have not been given formal names. In practice most cultigens are cultivars.
The following account of the historical development of cultivated plant taxonomy traces the way cultigens have arisen and been incorporated into botanical science; it also demonstrates how two approaches to plant nomenclature and classification have led to the present-day International Code of Nomenclature for algae, fungi, and plants and International Code of Nomenclature for Cultivated Plants.
Historical development
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 from the origin of the Cultivated Plant Code in 1953 until 2004.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 botanical nomenclature and classification 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, taxonomic botanist, classical scholar and author of the book Botanical Latin has commented that "cultivated plants 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 although their exact time and place of true origin will probably remain a mystery. Among the first cultigens would have been selections of the cereals wheat and barley that arose in the early settlements of the Fertile Crescent. Food plant selections would also have been made 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 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 are among the first known plant selections perpetuated in cultivation in the West. Migrating people would take their plant seeds and cuttings with them; there is evidence of early Fertile Crescent cereal cultigens being transferred from Western Asia to surrounding lands.
400 BCE to 1400 – the ancient world: Greco-Roman influence to the Middle Ages
As early as the 5th century BCE the Greek philosopher Hippo expressed the opinion that cultigens were produced from wild plants as the result of the care bestowed on them by man, a revolutionary view at a time when they were regarded as the special creation and gift of the gods. In devising ways of classifying organisms the philosopher Aristotle established the important idea of a fundamentum divisionis — the principle that groups can be progressively subdivided. This has been assumed in biological classification ever since and is congruent with the relatively recent idea of evolution as descent with modification. All biological classification follows this principle of groups within groups, known as a nested hierarchy, but this form of classification does not necessarily presuppose evolution. The earliest scientific approach to plants is attributed to Aristotle's student Theophrastus, known as the "father of botany". In his Enquiry into Plants Theophrastus described 480 kinds of plant, dividing the plant kingdom into trees, shrubs, undershrubs and herbs with further subdivision into wild and cultivated, flowering and non-flowering, deciduous or evergreen.The utilitarian approach, classifying plants according to their medicinal properties, is exemplified by the work of Roman nobleman, scientist and historian, Pliny the Elder author of Natural History. "Cultivars" listed here are named after people, places or special plant characteristics. Most notable is the work of Dioscorides a Greek doctor who worked with the Roman army. His five-volume Materia Medica was a forerunner of the herbal which led to the modern pharmacopoeia. This work was endlessly plagiarised by later herbals including those printed between about 1470 and 1670 CE: it listed 600 to 1000 different kinds of plants including the cultigens Gallica, Centifolia, the rose of uncertain origin known as Alba and other rose cultivars grown by the Romans.
The first record of a named cultigen occurs in De Agri Cultura. written about 160 BCE by Roman statesman Cato the Elder in a list that includes 120 kinds 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. Writers up to the 15th 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. For example, in 827 CE the following herbs were mentioned in the poem Hortulus by Walafrid Strabo as growing in the monastery garden of St Gallen in Switzerland: sage, rue, southernwood, wormwood, horehound, fennel, German iris, lovage, 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.