Guest Article RHODODENDRON UPDATE 1

  • Date: 12th March 2016
  • author: Francis Crome

INTRODUCTION

Our Society tries its best to keep ahead of developments in the Rhododendron world. You might think that one of the most basic things we would have is a checklist of world Rhododendron species; which ones are in Australia, and where, which ones are not and which of these are on ICON as Rhododendron species whose seed may be imported without a permit. The Society could then approach the government authority, DAFF, to enquire about whether those species not in Australia nor on the present list of species whose seed is permitted to be imported into Australia without a permit1 could be added to the list, after appropriate weediness vetting.

Unfortunately that is not the case. There is no definitive list of Rhododendron species of the world. If you ask even the simple question “how many species of Rhododendron are there?”, let alone “what are their names?”, you will get figures as low as 800 and as high as more than 1400.

There is a range of reasons for this. New species are constantly being discovered in the wild. Procedural issues of botanical nomenclature require change or modification of species names. Books and lists, unsurprisingly, occasionally make mistakes. One of the more frustrating issues is the fact that changes to taxonomy split or lump species regularly. These splits or lumps can be controversial and a “species” can flip flop backwards and forwards between being a species in its own right or merely a variety or subspecies some other species.

As, mostly amateur, enthusiasts our sources tend to be books. Volumes such as Argent (2006) for Vireyas, and Cox and Cox (1997), McQuire and Robinson (2009) and Davidian (1982, 1989, 1992 and 1995) for non Vireyas, are major sources2. Many changes have taken place since these volumes were written and in this and subsequent articles we will try to bring to your attention species mostly not covered in Argent (2006) and Cox and Cox (1997).

Rhododendron and horticultural societies worldwide are useful sources of information and we have searched these extensively. However, our most important sources for tracking down species have been the many on-line databases that have recently been developed. Table 1 lists the major ones we have used. The Plant List and IPNI have been our major sources. The Plant List is up to date to about 2011 and, although we found some errors, it provides a catalogue of the many names applied to Rhododendron. There are about 740 accepted names, 850 synonyms and 916 “unresolved”3 names (see Table 1).

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