Thymus nomenclature


For many years there has been a considerable amount of muddle in the naming of thymes.  Many herb nurseries still use common names rather than the correct binomial name, which can lead to a lot of confusion, for example golden thyme, lemon thyme and creeping thyme, all of which could refer to more than one cultivar.  I have been researching Thymus nomenclature since 1992, gradually sorting out correct names, working in consultation with The RHS Advisory Committee on Nomenclature and Taxonomy.  The results of this work have appeared each year in the new edition of the RHS Plant Finder.  I was appointed ICRA (International Cultivar Registration Authority) for Thymus in 2007 and published the International Thymus Register and Checklist in December 2009.

Searches through old nursery catalogues have revealed that new Thymus cultivars introduced by nurserymen, for example T. 'Dartmoor', T. 'Pink Ripple' and T. 'Ruby Glow', have at some time been incorrectly assigned to the species T. serpyllum.  I have checked herbarium specimens at Royal Botanic Gardens, Kew and the Natural History Museum, London and discovered that some of the species available in the nursery trade have been incorrectly named.  DNA studies carried out by my colleague Dr. Madan Thangavelu have enabled us to place many cultivars in the correct species.  In the course of preparation of the Register it became apparent that several cultivar epithets were either invalid or misapplied and new names were therefore necessary.  I have also been fortunate to have access to the RHS Lindley Library's extensive collection of old books, which enabled me to uncover and resolve the confusion over the status of the specific epithet in regard to lemon scented thyme.  This research led to my proposal that T. citriodorus should be regarded as a synonym of T. pulegioides and demonstrated that the lemon scented mid green bushy thyme of unknown parentage, together with its variegated cultivars, had been incorrectly included in T. citriodorus.

Since 2001 I have been publishing the results of my research on nomenclature in Plant Heritage and the original articles are archived in the Publications section for reference.  In this Nomenclature section there are separate sections for each main aspect of my research.  Individual cultivars which have been renamed, generally because of invalid or misapplied names, are included in the New Cultivar Names section.  The synonyms list includes UK, European and American cultivars and species readily available from nurseries, together with common names and is based on the synonyms list in the International Thymus Register and Checklist.

 Updated May 2010