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Horticultural Taxonomy
Why Plants Change Their Names
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"Why, oh why, do botanists keep changing the names of our garden plants?"
This topic is a very emotive issue, and we should be fully aware of the cost to the horticultural and other industries of any name changes. However, emotions must not outweigh serious scientific considerations, and adverse comments are often based on a lack of understanding or incorrect information.
There are many reasons why plants change their names, but basically these fall into three main types:
Taxonomy
Gardeners and nurserymen are mainly affected by taxonomic name changes which occur as a result of advances in botanical knowledge leading to a reclassification of plants. The great majority of cases happen when a plant is transferred from one higher taxon to another, e.g. a species to another genus, due to the reassessment of its position in a particular classification.
One cannot prevent the reclassification of plants into different genera, e.g. the common chrysanthemum has been put into Dendranthema, the genus Sedum is being split up, Zauschneria has been put into Epilobium, Pratia into Lobelia and Pernettya into Gaultheria. There are even whisperings of threats to lump Mahonia into Berberis! However, there are no botanical rules dictating which classification one should adopt and the above examples are still disputed by some botanists. Not long ago, the garden petunia was allowed to retain the Latin name Petunia, despite a proposal to place it in another genus.
Times are changing, and today the majority of botanists and taxonomists are working towards an objectively argued classification system. Many existing systems are somewhat artificial because they reflect the viewpoints of individual taxonomists, rather than attempting to show the pattern of the way plants actually evolved and how they are related to one another.
The adoption of such an improved system would benefit not only the plant breeder, but also all those looking for plant products and sources of beneficial characteristics, which may be found in closely related species. Name changes will therefore be inevitable as we move in this direction, but considerable flexibility exists within different classifications to permit a choice of correct names for one and the same taxon. In such cases, a broad consensus of views should be sought to find which names would be most widely accepted by the botanical community.
Misidentification
Name changes by misidentification occur when a plant comes into cultivation, is widely propagated and then distributed under the wrong name. A recent example is Sutera cordata, a charming ground cover plant from South Africa which was brought into Britain from Germany in mid-1992, either as Bacopa "Snowflake" or Sutera diffusa. Bacopa is a taxonomically different genus in the Scrophulariaceae, while Sutera diffusa is a made-up name and does not exist in the scientific literature!
Nomenclature
The other type of change is nomenclatural, i.e. where a name is found not to be in accordance with botanical rules. These occur more rarely with cultivated plants. They can be avoided only by the action of international committees, whose members are continually deciding how to avoid disadvantageous name changes.
Those involved in making these decisions have to take all viewpoints into account, and the end result is to promote stability of names, not changes. In the late 1970s, a common, shade-loving houseplant was allowed to keep the name Fittonia (1865), despite the existence of an older generic name Adelaster (1861).
In 1981, the International Botanical Congress voted to allow conservation of names in use for species of major economic importance and in certain other circumstances. One outcome of this was that the names of two commonly cultivated heathers, Erica carnea and E. vagans, were conserved.
At the 1993 International Botanical Congress in Toyko, the power of such committees was extended further so that:
it is now no longer necessary to prove major economic importance to have the name of a species conserved, and any name (at any rank) that might cause nomenclatural instability can now be proposed for rejection.