Changes to the scientific name of plants are part of life, though often frustrating. However, names are only changed for good reasons, and changes aim to give an accurate representation, not only of the true identity of a plant but also of its relationships. Some examples of why names are changed are given here.
1) Plants can be wrongly identified. For many years, a bedding plant was commonly grown under the name Helichrysum microphyllum. Its correct name, however, is Plecostachys serphyllifolia. Both species are in cultivation. The spider plant commonly referred to in the literature and grown in gardens as Cleome spinosa, is, in fact, a different species, C. hassleriana, now known as Tarenaya hhassleriana. The author ‘hot.’ (Latin hortulanorum, ‘of gardens’) is often used to denote plants that are grown in gardens under the incorrect name. In the example just given, Helichrysum microphyllum hot. (or at least hot. in part) is different to H. microphyllum (Willd.) Cambess.
2) Names can change for nomenclatural reasons. Nomenclature decides if he name used for a plant is the correct one— for example, it it was published correctly, or if there is an earlier name for the plant. The rules of nomenclature state that the earliest validly published name takes priority, even if this is obscure. Since the adoption of their use, many genera have been found to have earlier names, which should have been used. However, as changing the names of many familiar and important genera would cause considerable disruption, it has been possible to conserve these later names and allow their use. Pittosporum is an example of a conserved generic name. Without conservation, the earlier name Tobria would have been used.
The names of species can also be conserved, an important point when talking about those plants with a high profile in horticulture. As an example of this, Zinnia violate is an earlier name applied to the same species as Z. elegans. Under the rules of nomenclature, if they are regarded as the same species then Z. violate must take priority, as it was published first. However, as Z. elegans is a much more widely used name, it has been proposed for conservation. Many of these possible changes can therefore be avoided.
3) Names can change for taxonomic reasons. Taxonomy deals with the relationships between plants—for example, which genus does a particular plant belong in, or should it be regarded as a species, or maybe as a subspecies of a different species. There have always been name changes of this sort, but recent molecular work has made considerable advances in the understanding of plant relationships, resulting in many changes. It has been found, for instance, that most American species of Aster are not closely related to the Old World species, thus resulting in the splitting of the genus into several smaller ones.
Are these changes avoidable? In this example, it is not wrong to retain all species in the genus Aster, if, with good reason, it is believed that is where they should be, but the new classification shows better the relationships of the species involved, which can help gardeners and plant breeders. In addition, new species named may not have a useable name in the old genus. For example, the new species of Veronica have already been described from New Zealand and Australia with no name available for them in Hebe or Parahebe, or whichever genus they would have been assigned to in the past.
While conservation is a considerable help in promoting name stability, sometimes it comes at a price. When the genus Chrysanthemum was split into smaller genera, the generic names should have stayed with C. segeum (corn marigold) and its relatives, necessitating a new genus for the florists’ ‘mums’. As this would have caused considerable horticultural disruption, the genus Chrysanthemum was conserved so that the ‘mums’ would not have to change their name. This, however, necessitated moving the corn marigold and its relatives to another genus, Glebionis.
This post is excerpted from Plant Names Explained: Botanical Terms and Their Meaning by William Stern, Editors at Horticulture.
Image Credit: Photo Courtesy of Missouri Botanical Garden
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