International Thymus Register and Checklist - Author's Preface

I hold National Plant Collection^® of Thymus, granted Full Status in 1995 and Scientific Status in 2004 and run a backgarden nursery, LW Plants - Plants from a Plantsman's garden. A major aspect of being a Collection Holder is being aware of correct nomenclature and carrying out the necessary research. Since I started my research in 1992 and discovered the full extent of the muddle over Thymus nomenclature, in consultation with The RHS Advisory Committee on Nomenclature and Taxonomy, I have been sorting out names and renaming where necessary. The results of this work appear each year in the new edition of the RHS Plant Finder and I have published several articles relating to this research in Plant Heritage, the journal of Plant Heritage, formerly known as NCCPG. Although the new names are gradually becoming accepted by nurserymen and label manufacturers it is a slow process and it became obvious that a register was needed, to include not only thymes available from British nurseries, but also cultivars from America and Europe, many of which are now available in the UK. In 2007, with the support of Dr. Janet Cubey of the RHS, I applied to be appointed International Cultivar Registration Authority (ICRA) for Thymus and was appointed in late 2007, provisional until after the publication of the Register.

I began by going back to the Lindley Library's collection of nursery catalogues. I had first researched them in the early 1990s, but this time I photographed the relevant pages with my digital camera, so that I have a permanent record for reference. In addition to the catalogues, I have also used many of the books in the Lindley Library, again photographing the relevant pages for future reference. I also contacted my UK nurserymen friends for information, particularly Peter Foley, Arthur Shearing, John Tuite and Trevor Wood.

As far as the European cultivars are concerned, initially I used the PPP Index and Planten Vinder. My friend Roger Bastin sent me a lot of information on Dutch cultivars. I also contacted Gert Fortgens who gave me the link for his trial of Dutch cultivars at Boskoop Research Station in 1992, reported in Dendroflora. I had a short visit to Germany in the summer of 2008 to meet my friends Michael Camphausen and Herbert Vinken, to obtain information on German cultivars and discuss the problems regarding T. vulgaris French and other grey leaved variants of T. vulgaris, prior to publication of my autumn 2008 article in Plant Heritage (see T. vulgaris p. 127). Werner Simon sent me copies of his catalogues and also put me in contact with his colleague Klaus Oetjen. Werner's father, Hans Simon, introduced several thymes which he and Klaus had collected in the wild, as well as cultivars raised by Klaus. Some of the wild collected thymes which had been listed with invalid names have been renamed by Werner, Klaus and myself.

My American colleague Larry Hatch of New Ornamentals Society (NOS) gave me access to the Thymus section of the old NOS website, providing me with a starting point for American cultivars. Harriet Flannery wrote her thesis at Cornell University in 1982; A Study of the Taxa of Thymus Cultivated in the United States. Although it is still highly regarded by American nurserymen, many names are now out of date, particularly those for cultivars of creeping thyme, known at that time as T. praecox subsp. arcticus and which should now be regarded as cultivars of T. serpyllum. I contacted the Bailey Hortorium at Cornell University and Peter Fraissinet sent me a copy of the thesis and Peter Dirig arranged for the herbarium specimens to be sent to Royal Botanic Gardens, Kew for me to view them, together with all the other Thymus herbarium specimens in their collection. The thesis and herbarium specimens were invaluable for my research. The next stage was a Google search for each cultivar, checking nursery websites for information, followed by email contact with the nurseries. This was very successful and I received digital copies of catalogue pages, as well as information on the origins of cultivars from nurserymen, in particular from Francesco DeBaggio, David Hyde of Well-Sweep Herb Farm, Andy Van Hevelingen, Mark and Karen Langan of Mulberry Creek Herb Farm and Wanda Wulff of Bluebird Nursery. Betty Ann Addison posted her Rice Creek Gardens catalogues to me. Sherry Vance in the Bailey Hortorium at Cornell sent me a considerable number of photocopies of old catalogues in their collection and these enabled me to resolve earliest dates of publication for many cultivars. Larry Hatch and I needed to rename some American cultivars, where there was duplication of UK or European cultivar epithets. Where relevant this was done in consultation with the nurserymen raisers and where necessary new names have been published in my 2008 and 2009 Plant Heritage articles.

Another aspect of preparation of the Register related to resolving correct delineation at specific level, so cultivars can be placed in the correct species. In the course of my earlier research it became apparent that when Schreber and Persoon described T. citriodorus they were actually referring to lemon scented T. pulegioides and that the former should therefore be regarded as a synonym of the latter. Dr. Brent Elliott located the books in the Lindley Library on which they had based their citations and Craig Brough at Royal Botanic Gardens, Kew, assisted with books not in the Lindley Library collection. All the lemon scented cultivars of unknown parentage, previously included in T. citriodorus, have now been renamed without the specific epithet and validly published.

The Thyme Handbook was published by Plant Heritage in July 2009 and is for gardeners and nurserymen who love growing thyme. It includes about 100 species and cultivars readily available in the UK, compared with nearly 350 in the Register and the descriptions have been simplified. A combined publication of The Thyme Handbook and the International Thymus Register and Checklist will be available as a fully illustrated ebook, The Big Book of Thyme, in early 2010.

In The Thyme Handbook I proposed that all the creeping thyme of north west Europe should be regarded as T. serpyllum (see Nomenclature p. 10) and that hairy leaved creeping thyme should also be included in T. serpyllum. I was able to locate the specimen in the Druce Herbarium at Oxford which Ronniger used for his citation of T. pseudolanuginosus and discovered that it was less hairy than many of the wild specimens I have collected in England and Wales!

Throughout my research, besides my contacts with nurserymen and librarians, I have been guided by my botanist and nomenclature colleagues where necessary, especially Dr. Alan Leslie, Christopher Brickell and James Armitage. Where new names have been necessary, these have been in accordance with the current edition of the International Code of Nomenclature for Cultivated Plants (2004). As the Register includes the Coccineus Group as well as the species T. carnosus, T. pulegioides, T. serpyllum and T. vulgaris, with which I have been involved, it is to be known as the International Thymus Register and Checklist, rather than the Thymus Cultivar Register and Checklist.

It has proved impossible to find a validly published reference for some cultivars listed in early editions of Plant Finder, or in Index Hortensis, PPP Index and Planten Vinder and these are listed in the Appendix. However for such cultivars where habit, flower colour, leaf description, etc. are known, the names have been validly published in my 2008 and 2009 articles in Plant Heritage and are therefore included in the Register. It is proposed that new cultivar names will be published in Hanburyana in association with the RHS and should new information relating to cultivars currently listed in the Appendix become available these can also be registered by publication in Hanburyana.

My grateful thanks to the many people I have consulted and who have provided invaluable information which has enabled me to complete this work.

Easter, M. (2009) International Thymus Register and Checklist pp 5-7

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