abc logo Taxonomy of Rhododendrons
Rhododendron ABC's #4

By now, with 3 Rhododendron ABC's under our figurative belts, it is time to bear down and really try to find out how taxonomistshave divided our large and delightfully diverse Genus into groups or related species, so that one has at least a fighting chance of identifying and naming a specimen with which one is not familiar. (Don't give up, the whole subject is complex and authorities are still not completely satisfied that they can agree with each other!)

I will try to review what is now known and leave it at that. I then promise to shift to cultural requirements, siting of plants, pest control, pruning, etc.

It must be remembered that the modern general botanical naming system has been based on the scheme first proposed by Linnaeus about 200 years ago. This so-called natural system is based on the study of many traits but, in the main, is based on the reproductive nature of the plants collected in the wild. In so doing, taxonomists have come to arrange plant families in a natural order starting with those with 'primitive' traits and on to higher and more developed plants that have resulted from the passing of many, many thousands of generations. This system has worked well and there are now available numerous taxonomic 'keys' that allow one to identify pretty well most floral species found in the wild.

Nature, however, being sublimely indifferent to most human foibles, has presented us with some really tough classification problems with certain flowering plant families and genera by forming hundreds of species that are recognizably related, but which are obviously truly separate entities and are entitled to their own specific names. So it is with the Genus Rhododendron.

Until about 100 years ago, there was no real problem. Only a handful of rhododendron species were known and their identification was easy. Then came a period of the 'plant explorers'. Scores of obviously new species were collected by each exploration expedition and were sent back to herbaria (places that maintain collections of plant specimens for research and reference).

Most of the new collections were sent to herbaria in the UK In order to maintain some logical and systematic control, Balfourdevised what be called the series concept. Almost (but not quite) arbitrarily, Balfour divided the RhododendronGenus into some forty or so series, each named for a species which he felt was representative of each series. Then, by comparing vegetative traits, lie was able to assign species to their appropriate series based on their apparent affinities.

This scheme worked surprisingly well and it has endured even though it was not a natural, Linnean-type system. The series concept is still widely used by enthusiasts and one often sees references assigning a certain species based on its general resemblance to the key species of the series.

Certain taxonomists have come to believe that the Balfourian system is too artificial and too simplistic. Starting with Dr. Sleumer in the Netherlands, newer and more systematic schemes have now been devised and these are becoming more and more accepted. A complete description of the development of the newer systems is beyond the scope of our discussions, but in the next ABC's a short summary of the modern divisions of the Genus will be attempted.

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Dave Goheen