Thymus Nomenclature
I began researching Thymus nomenclature in 1992 and it soon became apparent that it was a complete muddle
and as more names were resolved, an even greater muddle was revealed.
As far as cultivars were concerned there seemed to be no consistency in the application of the specific epithet.
For example there was a bushy golden leaved thyme named T. vulgaris 'Aureus', which closely resembled the
golden leaved thyme collected by Bill Archer and at that time known as T. citriodorus 'Archer's Gold'.
However while the latter smelt of lemon, the former smelt of thyme.
There was also a bushy thyme with tiny pin-like golden leaves known as
T. caespititius 'Aureus', but this bore no resemblance to the species.
My initial reaction was to assume that someone had just reversed the labels.
In 1997 my colleague Dr. Madan Thangavelu carried out our first DNA study.
This demonstrated that T. caespititius 'Aureus' and another cultivar with golden pin-like leaves, known as
T. ericoides 'Aureus', were identical and should be regarded as a cultivar of T. vulgaris,
now known as T. vulgaris 'Golden Pins'.
There was also a white flowered thyme, with a bushy habit and pin-like leaves, wrongly placed in
T. richardii subsp. nitidus, a subspecies not known to be in cultivation.
When I had seen T. richardii subsp. ebusitanus and T. richardii subsp. richardii
growing at the Royal Botanic Gardens, Kew, both low growing woody shrubs with prostrate stems,
it was obvious that this white bushy thyme did not belong in this species.
As it keyed out as a cultivar of T. vulgaris and in view of its pin-like leaves, I decided to link its new name with
that of the golden leaved thyme and gave it the cultivar epithet 'Dorcas White', Dorcas being a brand name for dressmaking pins.
At the same time, the similar white flowered thyme, formerly known as T. compactus albus, an invalid name,
to which I had already given the cultivar epithet 'Snow White', was also included in T. vulgaris.
In 1999 Dr. Madan Thangavelu and I carried out the Golden Thyme DNA Study in which we demonstrated that the golden leaved thymes,
such as 'Archer's Gold' and 'Bertram Anderson' should be regarded as cultivars of T. pulegioides.
However I then had a problem with four cultivars, three of them with the epithet 'Aureus' and these had to be renamed.
The golden leaved cultivar retained the 'Aureus' epithet and the thyme previously known as T. vulgaris 'Aureus' became
T. pulegioides 'Goldentime,' as it smells of thyme.
Two cultivars had wrongly been assigned to T. serpyllum.
The golden leaved T. serpyllum 'Aureus' became T. pulegioides 'Elliott's Gold' in honour of Clarence Elliott who introduced it
and the lemon scented T. serpyllum 'Citriodorus' became T. pulegioides 'Lemon King'.
The Golden Thyme DNA Study also demonstrated that T. pulegioides, T. vulgaris and T. citriodorus hort. are distinct taxa.
Many incorrect names arise through simple mistakes, such as printing errors in catalogues,
mis-read hand written labels, or broken labels where part of the name goes missing.
The best example is the widely available compact creeping mat, pink flowered thyme, now correctly known as T. serpyllum 'Minor'.
The 'Minimus' epithet had arisen as a result of a printing error and because the Latin epithet was invalid after 1959
I was asked to rename it and in 2003 it became T. serpyllum 'Minimalist'.
This error was discovered in a more recently acquired collection of nursery catalogues at the Lindley Library.
The pale pink flowered creeping thyme, wrongly known as T. serpyllum 'Coccineus Minor', is another example
of a printing error and was renamed T. 'Alan Bloom' for the great plantsman who grew it.
Two thymes from the Netherlands have proved to be identical and it is likely that the epithet 'Rosalicht' is a misreading of the epithet 'Rosedrift',
bearing in mind that many Dutch nurserymen use English names for their plants.
Maybe the epithet 'Desboro' arose from a broken label on which the epithet 'Desborough' had been written
from the bottom up rather than the top down and the last three letters were lost!
Many names change because nurserymen ignore the original wishes of the raiser and alter the name.
Both John Tuite of West Acre Gardens and Trevor Wood of Southcombe Gardens have introduced many cultivars and their normal practice has been to use
a cultivar epithet without any specific epithet, but many of their introductions have incorrectly been placed in T. serpyllum.
Further research regarding the lemon scented thyme T. citriodorus has revealed that Persoon and Schreber cited earlier authors,
who had described lemon scented T. pulegioides and not the bushy mid green leaved, lemon scented thyme, currently included in
T. citriodorus, available from nurseries and garden centres, together with its cultivars such as 'Golden King'.
When Persoon described T. serpyllum citriodorus he was actually using the common name for T. pulegioides, Serpyllum,
as used by Parkinson and other authors, to describe lemon scented T. pulegioides.
It should be noted that there is no reference to hybrid status in either Persoon's or Schreber's citation.
This status only arose in 1924 when Ronniger, describing native British thymes, referred to T. citriodorus as a hybrid between
T. pulegioides and T. vulgaris, but only known as cultivated plants in England.
The thyme Ronniger was describing was the lemon scented garden thyme of unknown parentage and not the lemon scented T. pulegioides.
As the epithet citriodorus should be regarded as a synonym of T. pulegioides I have renamed the bushy mid green lemon scented thyme
T. 'Culinary Lemon' and the golden variegated cultivars are now better referred to without any specific epithet.
As far as the silver variegated cultivars are concerned, these are also better referred to without any specific epithet.
It has been confusing to have the identical looking cultivars, lemon scented 'Silver Queen'
in one species and thyme scented 'Silver Posie' in another.
The creeping thyme of north west Europe has been regarded by botanists as two distinct species.
Thymus serpyllum L., Breckland thyme in Britain, has hairs on all four sides of the stem.
The creeping thyme with hairs on only two sides of the stem has been renamed by botanists on a regular basis.
Ronniger in 1924 described T. drucei and T. britannicus.
Fournier in 1938 named it T. serpyllum subsp. britannicus, Jalas in 1970 named it T. praecox subsp. arcticus,
Holub in 1973 named it T. praecox subsp. britannicus, Debray in 1977 named it T. polytrichus subsp. arcticus
and finally in 1987 Kerguélen renamed it T. polytrichus subsp. britannicus.
However in my experience, both in collecting thyme throughout Britain and in growing it, there are far too many similarities across these two
so-called species, but in addition far too many dissimilarities within each so-called species.
Jalas in Flora Iranica in 1982 wrote, "Indumentum characters, including stem hairiness (whether hairy all round,
on two opposite sides or along the four angles alone), are of limited taxonomical value."
In 1970 Jalas, wrote "the true T. serpyllum L. em. Mill., a plant of the temperate and boreal zones of
vegetation, is totally absent from most of France, except in the northeasternmost parts of the country."
The creeping thymes I have seen in France and Austria are different from those growing in Britain, with longer stems and larger flowers.
In my opinion, based on studying the thymes which I have collected in the wild and grown for many years in the garden, the creeping thyme of Britain
should all be regarded as T. serpyllum rather than T. polytrichus subsp. britannicus, which more probably relates to
the wild creeping thymes of central Europe.
There are several cultivars with long prostrate stems which have been included in T. serpyllum, such as T. 'Lemon Curd'.
As they are more likely to be related to European Thymus species, they are also better referred to without any specific epithet.
As far as the hairy leaved thymes are concerned, I have observed both hairy and non-hairy creeping thymes growing side by side in the wild and
consider that it could be an adaptation to climatic conditions.
In Snowdonia the proportion of hairy leaved thyme is greater in plants growing at a higher altitude.
When examined with a hand lens it can be seen that the amount of hairiness on the leaves varies considerably.
The margins can be ciliate or just ciliate at the base, the upper surfaces vary from glabrous,
to sparsely covered with white hairs or thickly covered and the lower surfaces likewise.
Wilmott in 1923 considered Miller's 1768 T. lanuginosus a name of doubtful status
because of the inability to locate a type specimen in the herbarium of Miller.
Ronniger in 1924 described British woolly thyme as T. lanuginosus,
but in 1927 published the new name T. pseudolanuginosus for this thyme.
Harriet Flannery in her 1982 Thymus Study considered that there were insufficient grounds for designating Ronniger's
T. pseudolanuginosus as an independent species and proposed the cultivar epithet 'Lanuginosus' within
T. praecox subsp. arcticus.
However in view of the fact that there is such a wide variation in the amount of hairiness present in wild thyme populations
and it is next to impossible to delineate between the hairy and non-hairy creeping thymes,
I therefore propose that they should all be regarded as T. serpyllum.
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