The Garden
February 2002

New conifer discovered

A new species of conifer has been discovered in Vietnam, giving rise to a new genus and some name changes, including the botanical name for x Cupressocyparis leylandii (Leyland cypress). Xanthocyparis vietnamensis (golden Vietnamese cypress) is the first new genus of conifer to be found since Wollemia nobilis was discovered in Australia in 1994, and only the third since 1948. Image: Royal Botanic Gardens, Kew

The tree was found growing on inaccessible cliffs and ledges in an area of karst scenery in 1999; the area where the tree grows is heavily wooded and subject to high rainfall. It was discovered by an international team of botanists from the Royal Botanic Gardens, Kew, the Missouri Botanical Garden, USA, the Vietnamese Institute for Terrestrial Ecology in Hanoi and the Komarov Botanical Institute in St Petersburg, Russia. Image: Phillip Cribb

Samples of the plant were collected in 1999 by a Vietnamese botanist and sent to Dr Aljos Farjon, Taxonomist for Gymnosperms at Royal Botanic Gardens, Kew, and author of the World Checklist and Bibliography of Conifers (RGB Kew, 1998). Farjon suspected that the plant could be a new species and asked the team to collect more samples. These confirmed that the plant from Vietnam was indeed a species new to science. Seed is currently unavailable and it has therefore proved impossible to determine whether the tree is hardy in a temperate climate.

All known examples of X. vietnamensis are relatively small trees, reaching a maximum height of 15m (50ft). The soil is very thin and it quite possible that the species can grow to a greater height. The steep ridge where the trees occur is an area of high bio-diversity, surrounded by intensively managed farmland. Orchids abound in the surrounding forest and they account for the majority of the ground flora.

Mature trees are unusual in having two types of foliage - some branches have flat, scale-like leaves, similar to those of Chamaecyparis, while others have linear leaves with pointed tips.

Although X. vietnamensis is producing fertile seed and regenerating, there are concerns about its future. Forests here have been exploited for timber and, while confined to inaccessible situations, only a few hundred X. vietnamensis remain. The team failed to find any other specimens in the area.

The biggest threat to the tree comes from the indigenous people, who harvest the local forests for firewood. Meanwhile, scientists analysing Chamaecyparis nootkatensis (Nootka cypress) have demonstrated that it is distinct from other members of the genus Chamaecyparis, and, according to research by Farjon and his collaborators, it is closely related to the new Vietnamese conifer. It has therefore been transferred to the new genus and becomes Xanthocyparis nootkatensis. Because one of its parents has been reclassified, x Cupressocyparis leylandii, a hybrid between Nootka cypress and Cupressus macrocarpa, must now be renamed. The new name of this infamous and controversial plant becomes x Cuprocyparis leylandii.

Aljos is currently working on the taxonomy of the family Cupressaceae. Cladistic analysis of its morphology has shown that Chamaecyparis nootkatensis (the Nootka cypress) is distinct from other members of the genus and it has therefore has been transferred to a new genus, Xanthocyparis. This decision has been confirmed by DNA analysis. The cladistic analysis demonstrated that the new Vietnamese tree was closely related to X. nootkatensis and it has subsequently been named Xanthocyparis vietnamensis. The transfer of Chamaecyparis nootkatensis to the new genus means that the infamous x Cupressocyparis leylandii must now be renamed x Cuprocyparis leylandii. The discovery that Leyland's cypress is truly an intergeneric hybrid may explain why it is sterile.

A formal description of the new species will be published in the journal Novon during the early part of 2002. The paper will be entitled A new genus and species in Cupressaceae (Coniferales) from Northern Vietnam.

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