Zelkova carpinifolia (Caucasian elm)
Zelkova carpinifolia at Kew Gardens
Zelkova carpinifolia (Pall.) K.Koch
Caucasian elm, ironwood
Threatened (NT) according to IUCN Red List criteria.
About this species
Caucasian elm is highly valued as an ornamental owing to its unusual outline, having a relatively short, wide trunk that divides into many ascending branches. It has been described as goblet-, vase- or broom-shaped. This unique tree is slow-growing but long-lived, and its girth increases markedly with age.
Caucasian elm is a member of the elm family (Ulmaceae) but Zelkova species differ from true elms (Ulmus species) in that their bark is smooth.
Geography and distribution
Caucasian elm is, as its name suggests, native to the Caucasus (a mountainous region of southeast Europe and southwest Asia), including Armenia, Azerbaijan, Georgia, Iran and Turkey.
Overview: A tree growing up to 35 m tall, Caucasian elm has a trunk that usually divides into many upright branches just 3–6 metres above the ground. It has smooth, grey bark that sometimes peels off in flakes. The young branches have a dense covering of short, soft hairs.
Leaves: Are thick, dark green on the upper surface, paler on the lower surface and have bluntly toothed edges.
Fruits: About 8 mm in diameter with a ridged surface.
Threats and conservation
Caucasian elm has been extensively logged locally for its timber, which is considered to be attractive. As a result, it is rare in many regions and listed as Near Threatened according to IUCN Red List criteria. In Turkey, for example, only a few highly isolated populations are known.
A long-lived tree with an unusual broom-like shape and leaves that turn golden orange in the autumn, Caucasian elm is cultivated as an ornamental. Its wood is hard, durable, flexible and rot-resistant. Although it has been extensively used in some localities, for example in the construction of door and window frames, it is not generally exported. This may be because the short trunk and relatively thin branches limit the length of useful timber that can be obtained.
A history of the Caucasian elm at Kew
Three specimens of Caucasian elm were originally planted at Kew in 1760 when zelkovas were reportedly brought into cultivation in Britain. Planted in what is now the Herbarium paddock, they were not listed as notable historic trees in the 1905 survey but were measured as being 18 m high even then.
Little seems to be known about these specimens, even under all their previous scientific names, including Zelkova crenata. Because they are not within the boundaries of the original arboretum, it is unlikely they were bought by Princess Augusta for the original botanic garden at Kew. Indeed, the paddock where they are planted was once the garden of a neighbouring house. It is possible that only a few zelkovas were introduced around this time, whereas more were brought in from Persia by the French botanist André Michaux around 1782.
In 1905, the British naturalist Henry John Elwes and Irish plantsman Augustine Henry noted that ‘this tree is now rarely seen in nurseries, though it is easily propagated by suckers and seed could be procured without difficulty from its native country’. They may have been brought in from France where they were admired and collected or they may have been donated by an estate in Britain that already had one - for example the tree at Wardour Castle was thought to have been one of the first in the country and was measured at 30 m high in 1905.
Millennium Seed Bank: Saving seeds
The Millennium Seed Bank Partnership aims to save plant life worldwide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
One collection of Zelkova carpinifolia seeds is stored in Kew’s Millennium Seed Bank based at Wakehurst in West Sussex.
This species at Kew
A superb specimen of Caucasian elm can be seen in the Herbarium paddock at Kew (an area just outside the publicly accessible gardens). This tree is thought to be the lone survivor of three planted in this area in 1760. A Caucasian elm can also be seen growing in the area between the Orangery and Elizabeth Gate; this tree was planted in 2009 as part of Kew’s 250th year celebrations.
Pressed and dried specimens of Zelkova carpinifolia are held in Kew’s Herbarium where they are available to researchers by appointment.
Specimens of the wood, bark and roots of Caucasian elm are held in Kew’s Economic Botany Collection in the Sir Joseph Banks Building.
Kew's 'Old Lions'
Kew’s ‘Old Lions’ are some of the few remaining trees with the oldest actual known planting date of 1762. They comprise: Ginkgo biloba (maidenhair tree), Styphnolobium japonicum (pagoda tree) and Platanus orientalis (oriental plane) to the west of the Princess of Wales Conservatory; Robinia pseudoacacia (black locust) on the lawn to the front of the Orangery; and Zelkova carpinifolia (Caucasian elm) situated in the Herbarium paddock.
Some of these trees were brought from a neighbouring estate at Whitton which belonged to the Duke of Argyll (the uncle of Lord Bute, the botanical advisor to Princess Augusta). They became part of a new five-acre arboretum, laid out by William Aiton, which sat next to the Orangery.
Now, 250 years after these trees were planted, Kew is celebrating the ‘Old Lions’, which can be seen in all their splendour, still growing in the Gardens.
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Andrews, S. (1994). Tree of the year: Zelkova. International Dendrology Society Yearbook 1993: 11–30.
Güner, A. & Zielinski, J. (1998). Zelkova carpinifolia. In: IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 30 April 2012.
Huxley, A., Griffiths, M. & Levy, M. (eds) (1997). The New Royal Horticultural Society Dictionary of Gardening. Volume 4 (R to Z). Macmillan Reference, London.
Kozlowski, G., Gibbs, D., Huan, F. & Frey, D. (2012). Conservation of threatened relic trees through living ex situ collections: lessons from the global survey of the genus Zelkova (Ulmaceae). Biodiversity and Conservation 21: 671–685.
Mabberley, D. J. (2008). Mabberley’s Plant-book: a Portable Dictionary of Plants, their Classification and Uses. Third edition. Cambridge University Press, Cambridge.
The Plant List (2010). Zelkova carpinifolia. (Accessed 30 April 2012). Available online.
Kew Science Editor: Emma Tredwell
Kew contributors: Melanie Thomas
Copyediting: Emma Tredwell
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