Floating golden cypress
Derrick Rooney, New Zealand Tree Grower May 2005
Last year, the news broke that a previously unknown species of conifer had been found among the remnants of moist karst forest in northern Vietnam.
The new tree was dubbed as the golden Vietnamese cypress, and a new genus – Xanthocyparis – was erected to accommodate the species, which was subsequently described as Xanthocyparis vietnamensis.
Just not perfectly matched
Some 54 morphological characters, as well as DNA evidence, were used to place Xanthocyparis vietnamensis as a sister species to the Nootka cypress, Chamaecyparis nootkatensis, also known as Alaskan yellow cedar. The latter was subsequently transferred to the new genus. This led to the renaming of three inter-generic hybrids, one of which is the well-known Leyland cypress, now very widely planted in New Zealand. The other two are Cuprocyparis ovensii, a hybrid with the Mexican cypress, Cupressus lusitanica, and Ferndown – a Nootka-Arizona cypress cross.
The name Xanthocyparis, which translates as golden cypress, seemed perfectly matched to the Nootka cypress as well, given the yellowish tones of its sawn timber. Alas for the new name, the honeymoon is over and annulment proceedings are already completed. Further research has revealed that under the taxonomic rules of the International Code of Botanical Nomenclature, the new genus is invalid and cannot stand.
Another obscure name
Since its discovery by naturalists in Alaska and far western Canada in the 18th century, the Nootka cypress has had a chequered career, drifting from Cupressus to Chamaecyparis and back to Cupressus before seeming finally to settle in Xanthocyparis. The new research has uncovered yet another very obscure name, Callitropsis nootkatensis, dating from 1865 and apparently overlooked by the taxonomists who erected the new golden-cedar genus. Under the international rules, this name being older has priority over the new name Xanthocyparis.
Because the golden Vietnamese cypress and the Nootka cypress are sister taxa and appear to be closely allied, both have been transferred to the genus Callitropsis, which now contains two species widely separated by geography. These are Callitropsis nootkatensis native to north-western North America, and C. vietnamensis native to moist karst forest in northern Vietnam.
Yellow cedar by any other name
There is no word yet about the future of the Leyland cypress, which in the last few years has wobbled from Cupressocyparis to Cupressus and then to Cuprocyparis, the last name having been published just last year. Presumably it and the other inter-generic hybrids will now move, in due course and with luck for the last time, to something like Cupressitropsis or Cuprotropsis, or who knows what.
If all this proves anything, it is simply that, where plants of any kind are concerned, knowledge expands to accommodate available data. After all, a rose under any name is still a rose, and a yellow cedar under any name still grows like a yellow cedar.