Ulmus glabra

Ulmus glabra
Wych elm
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Rosales
Family: Ulmaceae
Genus: Ulmus
Species: U. glabra
Binomial name
Ulmus glabra
Huds.
Synonyms
  • Ulmus campestris L. Mill., Wilkomm
  • Ulmus corylacea Dumrt.
  • Ulmus elliptica Koch
  • Ulmus effusa Sibth.
  • Ulmus excelsa Borkh.
  • Ulmus expansa Rota
  • Ulmus leucocarpa Schur.
  • Ulmus macrophylla Mill.
  • Ulmus major Sm.
  • Ulmus montana Stokes, Smith, Loudon, Mathieu, With.
  • Ulmus nuda Ehrh.
  • Ulmus podolica (Wilcz.) Klok.
  • Ulmus popovii Giga.
  • Ulmus scabra Mill., C. K. Schneid., Ley, Ascherson & Graebner
  • Ulmus scotica Gand.
  • Ulmus suberosa Michx.
  • Ulmus sukaczevii Andronov

Ulmus glabra, the wych elm or Scots elm, has the widest range of the European elm species, from Ireland eastwards to the Urals, and from the Arctic Circle south to the mountains of the Peloponnese in Greece; it is also found in Iran. A large, deciduous tree, it is essentially a montane species, growing at elevations <1500 m, preferring sites with moist soils and high humidity.[1] The tree can form pure forests in Scandinavia and occurs as far north as latitude 67°N at Beiarn in Norway. Wych elm has also been successfully introduced to Narsarsuaq, near the southern tip of Greenland (61°N).

The tree was by far the most common elm in the north and west of the British Isles and is now acknowledged as the only indisputably British native elm species. Owing to its former abundance in Scotland, the tree is occasionally known as the Scotch or Scots elm.

Closely related species, such as Bergmann's Elm U. bergmanniana and Manchurian Elm U. laciniata, native to northeast Asia, were once sometimes included in Ulmus glabra;[2] another close relative is the Himalayan or Kashmir Elm U. wallichiana.

Etymology

The word wych has its origins in Middle English wiche, from the Old English wice, meaning pliant or supple, and which also gives us wicker and weak.

Classification

Subspecies

Some botanists, notably Lindquist [3] (1931) have proposed dividing the species into two subspecies:

However, there is much overlap between populations with these characters, and the distinction may be owing to environmental influence, rather than genetic variation; the subspecies are not accepted by Flora Europaea.[4]

Description

The wych elm sometimes reaches heights of 40 m, typically with a broad crown where open-grown, supported by a short bole < 2 m. d.b.h. There are not normally root suckers; natural reproduction is by seed alone. The tree is notable for its very tough, supple young shoots, which are always without the corky ridges or 'wings' characteristic of many elms. The alternate leaves are deciduous, 6–17 cm long by 3–12 cm broad, usually obovate with an asymmetric base, the lobe often completely covering the short (<5 mm) petiole; the upper surface is rough. Leaves on juvenile shoots sometimes have three or more lobes near the apex.[5] The perfect hermaphrodite flowers appear before the leaves in early spring, produced in clusters of 10-20; they are 4 mm across on 10 mm long stems and, being wind-pollinated, are apetalous. The fruit is a winged samara 20 mm long and 15 mm broad, with a single, round, 6 mm seed in the centre, maturing in late spring.[6][7]

Pests and diseases

While the species is highly susceptible to Dutch elm disease,[8][9] it is less favoured as a host by the elm bark beetles which act as vectors. Research in Spain has indicated the presence of a triterpene, alnulin, renders the tree bark less attractive to the beetle than the Field elm.[10] Moreover, once the tree is dying, its bark is quickly colonized by the fungus Phoma, which radically reduces the amount of bark available for the beetle to breed on.[11] In European trials, clones of apparently resistant trees were inoculated with the pathogen, causing 85 – 100% wilting, resulting in 68% mortality by the following year. DNA analysis by Cemagref (now Irstea) in France has determined the genetic diversity within the species is very limited, making the chances of a resistant tree evolving rather remote.[12]

The Swedish Forest Tree Breeding Association at Källstorp produced triploid and tetraploid forms of the tree, but these proved no more resistant to Dutch elm disease than the normal diploid form. [13]

In trials conducted in Italy, the tree was found to have a slight to moderate susceptibility to elm yellows, and a high susceptibility to the elm leaf beetle Xanthogaleruca luteola .[14]

Cultivation

The wych elm is moderately shade-tolerant, but requires deep, rich soils as typically found along river valleys.[15] However, the species is intolerant of flooding, as it is of prolonged drought.[16] Although rarely used as a street tree owing to its shape, it can be surprisingly tolerant of urban air pollution, constricted growing conditions and severe pollarding.

As wych elm does not sucker from the roots, and any seedlings are often consumed by uncontrolled deer populations, regeneration is very restricted, limited to sprouts from the stumps of young trees. The resultant decline has been extreme, and the wych elm is now uncommon over much of its former range. It is best propagated from seed or by layering stooled stock plants, although softwood cuttings taken in early June will root fairly reliably under mist.[17]

Notable trees

Wych elms flanking the Scott Monument, Princes Street Gardens, Edinburgh, 2010

The UK Champion listed in The Tree Register of the British Isles (TROBI) is at Brahan in the Scottish Highlands;[18] it has a girth of 703 cm (2.23 m d.b.h.) and a height of 24 m . Outside the Brighton area, among the rare survivors in the south of England (2014) is a mature tree at the University College sports ground, Abingdon Road, Oxford. Notable specimens in Edinburgh are to be found (2014) in Learmonth Gardens and The Meadows.[19]

E. M. Forster cites a particular wych elm, one that grew at Rooks Nest, Stevenage, Hertfordshire, sixteen times in his novel Howards End. This tree overhangs the house of the title and is said to have a “....girth that a dozen men could not have spanned..” Forster describes the tree as “...a comrade, bending over the house, strength and adventure in its roots.” The wych elm of the novel had pigs' teeth embedded in the trunk by country people long ago and it was said that chewing some of the bark could cure toothache. In keeping with the novel's epigraph, "Only connect...", the wych elm may be seen by some as a symbol of the connection of humans to the earth. Margaret, the novel's protagonist, fears that any “....westerly gale might blow the wych elm down and bring the end of all things...” The tree is changed to a chestnut in the 1991 film adaptation of Howards End.

In 1998, over 700 healthy, mature trees were discovered on the upper slopes of Mount Šimonka in Slovakia, but it is now believed they had survived courtesy of their isolation from disease-carrying beetles rather than any innate resistance; 50 clones of these trees were presented to HRH The Prince of Wales for planting at his Highgrove Estate, and at Clapham, Yorkshire .

Cultivars

About 40 cultivars have been raised, although at least 30 are now probably lost to cultivation as a consequence of Dutch elm disease and/or other factors:

Camperdown elm, cultivated in Prospect Park, Brooklyn, New York

Some elm cultivars of unconfirmed derivation, such as the Exeter Elm and the dwarf elm 'Nana', were classified until recently as forms of U. glabra.

Hybrids and hybrid cultivars

U. glabra hybridises naturally with U. minor, producing elms of the Ulmus × hollandica group, from which there have arisen a number of cultivars:

A crossing in Russia of U. glabra and U. pumila, the Siberian Elm, produced the hybrid Ulmus × arbuscula.

Hybrids with U. glabra in their ancestry have featured strongly in recent artificial hybridization experiments in Europe, notably at Wageningen in the Netherlands, and a number of hybrid cultivars have been commercially released since 1960.[20] The earlier trees were raised in response to the initial Dutch elm disease pandemic that afflicted Europe after the First World War, and were to prove vulnerable to the much more virulent strain of the disease that arrived in the late 1960s. However, further research eventually produced several trees effectively immune to disease, which were released after 1989.[21]

Accessions

North America
Australasia

Nurseries

North America

Only as cultivar 'Camperdownii' (Camperdown elm)

Europe

Widely available - in the UK, nurseries stocking this tree can be found by using the plantfinder function of the Royal Horticultural Society's website. This tree is also stocked by many local nurseries and by the British Trust for Conservation Volunteers.

Further reading

References

  1. ↑ Heybroek, H. M., Goudzwaard, L, Kaljee, H. (2009). Iep of olm, karakterboom van de Lage Landen (:Elm, a tree with character of the Low Countries). KNNV, Uitgeverij. ISBN 9789050112819
  2. ↑ Elwes, H. J. & Henry, A. (1913). The Trees of Great Britain & Ireland. Vol. VII. 1848–1929. Republished 2014 Cambridge University Press, ISBN 9781108069380
  3. ↑ Lindquist, B. (1931). Two varieties of North West European Ulmus glabra. Bot. Exch. Club Rep.
  4. ↑
    Wikimedia Commons has media related to Ulmus glabra.
    Flora Europaea: Ulmus glabra
  5. ↑ Coleman, M (ed.). (2009). Wych Elm. Royal Botanic Garden Edinburgh. ISBN 978-1-906129-21-7.
  6. ↑ Bean, W. J. (1981). Trees and shrubs hardy in Great Britain, 7th edition. Murray, London.
  7. ↑ White, J. & More, D. (2003). Trees of Britain and Northern Europe. Cassell's, London
  8. ↑ Forestry Commission. Dutch elm disease in Britain, UK
  9. ↑ Brasier, C. M. (1996). New horizons in Dutch elm disease control. Pages 20–28 in: Report on Forest Research, 1996. Forestry Commission. HMSO, London, UK.
  10. ↑ Martín-Benito D., Concepción García-Vallejo M., Alberto Pajares J., López D. 2005. Triterpenes in elms in Spain. Can. J. For. Res. 35: 199–205 (2005).
  11. ↑ Webber, J. (1980). A natural biological control of Dutch elm disease. Nature, 292, 449-451
  12. ↑ Solla et al. (2005). Screening European Elms for Resistance to Ophiostoma novo-ulmi. Forest Science, 134–141. 51 (2) 2005. Society of American Foresters.
  13. ↑ Went, J. (1954). The Dutch Elm Disease - Summary of fifteen years' hybridization and selection work (1937–1952). European Journal of Plant Pathology. 02(1954); 60(2): 109–1276.
  14. ↑ Mittempergher, L. & Santini, A. (2004). The History of Elm Breeding. Invest. Agrar.: Sist Recur For. 2004 13 (1), 161-177.
  15. ↑ Edlin, H. L. (1949). British woodland trees. Batsford, London.
  16. ↑ CAB International (2005) Forestry Compendium. CAB International, Wallingford, UK
  17. ↑ Beckett, K. & G. (1979). Planting Native Trees and Shrubs. Jarrold & Sons, Norwich, UK.
  18. ↑ The Brahan Elm, forestry.gov.uk
  19. ↑ Edinburgh Wych-elm photographs
  20. ↑ Green, P. S. (1964). Registration of cultivar names in Ulmus. Arnoldia. Vol. 24. Arnold Arboretum, Harvard University.
  21. ↑ Heybroek, H. (1983). The Dutch elm breeding program. In Sticklen & Sherald (Eds). Dutch elm disease research (Ch. 3). Springer Verlag, New York.

External links