Winter Tree Highlights
The cypress family, Cupressaceae, is one of the most commonly encountered in parks and gardens, represented by a relatively small number of species but a wealth of cultivars and hybrids of all shapes and sizes, with no shortage of different colours.
The world’s largest tree by volume – giant redwood, Sequoiadendron giganteum – and also the world’s tallest – coast redwood, Sequoia sempervirens – are also members of the cypress family. As well as these more common trees, the family contains a number of genera that are rather less well known, but no less significant. A number of these are also monotypic (i.e. the genus contains only one species) and are an important component of the Westonbirt collection.
Golden Vietnamese Cypress
The golden Vietnamese cypress, Xanthocyparis vietnamensis, is fantastically interesting. This is partly because its discovery in 1999 led to the describing of a new genus, including this species and Nootka cypress, X. nootkantensis, transferred from Chamaecyparis as a result of this discovery. It is unusual for often having juvenile, transitional and mature foliage on branches of mature trees. This character is found only naturally in a small number of other trees. Native to parts of north Vietnam and southern China, it was introduced in the early 2000s and plants are proving to be hardy at Westonbirt, thus far.
Golden Vietnamese cypress – we have over a dozen plants in the collection now and are observing their performance in different conditions across the site.
The Chinese arbor-vitae, Platycladus orientalis, is closely related to the genus Thuja, which contains the well-known western red cedar, T. plicata, and was originally placed within this genus. However, it differs from Thuja in foliage and fruit, with the presence of the latter always useful in determining genera in the cypress family. In foliage, the two genera can be separated by the leaf sprays of the Chinese arbor-vitae with both sides indistinguishable from each other, whereas Thuja have paler, sometimes white undersides. The foliage of Thuja species is aromatic when crushed, whilst that of Chinese arbor-vitae is pretty odourless. It’s always worth having a sniff!
Chinese arbor-vitae – as well as growing well at Westonbirt, it is widely grown in many parts of the world. Native to Asia, it is difficult to establish its true natural range due to its ability to spread.
All three members of the cypress family native to South America are represented at Westonbirt. They also all belong to monotypic genera. One of these, Chilean cedar, Austrocedrus chilensis, has an interesting characteristic, in that whilst it can grow with a rounded crown in the wild, in cultivation it has a rather fastigiate habit; i.e. the branches grow parallel to the main stem of the plant. This feature is shared with other members of the cypress family, including the Incense cedar, Calocedrus decurrens. Our examples are all young trees and we hope that they eventually perform a similar role to that of the incense cedar in the landscape in years to come.
Chilean cedar – though commonly known as a ‘cedar’, it is not in closely related to the true cedars in the genus Cedrus. Common names can be confusing!
The second of the South American trio is alerce, Fitzroya cupressoides. Like many coniferous species, it is threatened with extinction in its native habitat and is classified as Endangered on the IUCN Red List of Threatened Species. It is also listed on Appendix 1 of the Convention on International Trade in Endangered Species (CITES). A third of cypress family representative from South America, Pilgerodendron uviferum, are also included in this list, with international trade of these species banned. Until recently, genetic stock of alerce in cultivation was very narrow. The work of the International Conifer Conservation Programme, led by RBG Edinburgh, has somewhat boosted this and as a partner organisation, we grow plants as part of this initiative.
Alerce – some botanists believe this species to be the second-longest living trees on Earth. The trees wouldn't look out of place in Jurassic Park!
Clues to the identification of plants are often in the name, and the specific epithet of Taiwania cryptomerioides denotes its likeness to another member of the cypress family, Japanese cedar, Cryptomeria japonica. It is the juvenile foliage of the Taiwania cryptomerioides that resembles the adult foliage of Japanese cedar, with no examples in UK cultivation yet to develop adult foliage. One of our young plants is growing particularly well, though while it grows to 60 metres in its native Taiwan, we might be a little too optimistic to expect it to attain the same stature here!
Taiwania – The genus is named after the island of Taiwan, from where it first became known to the botanical community in 1910.