Ulmus laevis

Ulmus laevis
European White Elm in winter Llandegfan, Anglesey
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Rosids
Order:	Rosales
Family:	Ulmaceae
Genus:	Ulmus
Species:	U. laevis
Binomial name
Ulmus laevis Pall.
Synonyms
Ulmus acuta Dumrt. Ulmus ciliata Ehrh. Ulmus effusa Willd., Loudon, Willkomm, Fliche Ulmus laevis var. celtidea Rogowicz Ulmus laevis var. simplicidens (E. Wolf) Grudz. Ulmus octandra Schkuhr Ulmus pedunculata Foug. Ulmus petropolitana Gand. Ulmus racemosa (not Thomas), Borkh. Ulmus reticulata Dumrt. Ulmus simplicidens E. Wolf

Ulmus laevis Pall., called the European White-elm,^[1] Fluttering Elm, Spreading Elm, Stately Elm and Russian Elm, is a large deciduous tree native to Europe, from France^[2] northeast to southern Finland, east as far as the Urals, and southeast to Bulgaria and the Crimea; there is also a disjunct population in the Caucasus. Moreover, a small number of trees found in Spain is now considered a relict population rather than an introduction by man, and possibly the origin of the European population.^[3]

Endemic to alluvial forest, U. laevis is rarely encountered at elevations above 400 m.^[4] Most commonly found along rivers such as the Volga and Danube, it is one of very few elms tolerant of prolonged waterlogged, anoxic ground conditions. Although not possessed of an innate genetic resistance to Dutch elm disease, the species is rarely infected in western Europe. The White Elm is allogamous and is most closely related to the American Elm U. americana. Not a native of the United Kingdom, U. laevis was first offered for sale by an Exeter nursery in 1836.

Description

The tree is similar in stature to the Wych Elm, if rather less symmetric, with a looser branch structure and less neatly rounded crown. It typically reaches a height and breadth of > 30 m, with a trunk < 2 m d.b.h. The extensive shallow root system ultimately forms distinctive high buttresses around the base of the trunk. The leaves are deciduous, alternate, simple ovate with a markedly lop-sided base, < 10 cm long and < 7 cm broad, comparatively thin, often almost papery in texture and very translucent, smooth above with a downy underside. The apetalous wind-pollinated flowers appear before the leaves in early spring, produced in clusters of 15-30; they are 3–4 mm across on 20 mm long stems. In England, trees grown from seed flower in March, commencing at ages of between 7 and 12 years.^[5] The fruit is a winged samara < 15 mm long by 10 mm broad with a ciliate margin, the single round 5 mm seed maturing in late spring. U. laevis sheds its leaves earlier in the autumn than other species of European elm.

The tree is most reliably distinguished from other European elms by the long flower stems, and is most closely related to the American Elm U. americana, from which it differs mainly in the irregular crown shape and frequent small sprout stems on the trunk and branches, features which also give the tree a winter silhouette; a useful diagnostic feature at this season.^{[6] [7]} Although the species is protandrous, levels of self-pollination are high^[8] The tree can grow very rapidly; where planted in persistently moist soil, trunk width of 13-year-old trees increased by 4 cm per annum at breast height (d.b.h.). ^[9]

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  Surface root structure exposed by bank erosion

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  U. laevis buttresses

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  U. laevis flowers; note long stems

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  U. laevis seeds

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  Ulmus laevis leaf

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  U. laevis autumn colour

Pests and diseases

Like other European elms, natural populations of the European White Elm have little innate resistance to Dutch elm disease, although research by Irstea has isolated clones able to survive inoculation with the causal fungus, initially losing < 70% of their foliage, but regenerating strongly the following year.^[10] Moreover, the tree is not favoured by the vector bark beetles, which colonize it only when there are no other elm alternatives available,^[11] an uncommon situation in western Europe. Indeed, in a study of elm in Flanders, not one example of U. laevis was found to be afflicted by Dutch elm disease. ^[12] Research in Spain^[13] has indicated that it is the presence of a triterpene, alnulin, that renders the tree bark unattractive to the beetles. Ergo: the tree's decline in western Europe is chiefly owing to woodland clearance in river valleys, not disease.

The species has a slight to moderate susceptibility to Elm Yellows, but a very low susceptibility to the elm leaf beetle Xanthogaleruca luteola.^[14]

Cultivation

U. laevis is essentially a riparian tree, able to withstand over 100 days of continual flooding. ^[15] Spanish trees were found to be calcifuge, preferring slightly acid, siliceous soils, and also drought-intolerant, their xylem vessels prone to drought-stress cavitation. ^[16] However, healthy trees approximately 100 years old were discovered in England planted around an ammunition dump on the elevated chalk of Salisbury Plain about 2 km from Stonehenge. The tree is comparatively weak-wooded, much more so than Field Elm Ulmus minor, and thus an inappropriate choice for exposed locations. In trials in southern England by Butterfly Conservation, young trees of <5 m height were badly damaged by gusts of 40 knots (75 km/h) in midsummer.^[5]

The species was never widely introduced to the USA, but is represented at several arboreta. In the Far East, the tree has been planted in Xinjiang province and elsewhere in Northern China; planting in Tongliao City is known to have been particularly successful. White Elm is also known to have been introduced to Australia.^[17]

In recent years, the tree has enjoyed a small renaissance in England. A popular larval host plant of the White-letter Hairstreak Satyrium w-album butterfly across Europe, the elm is now being planted by Butterfly Conservation and other groups to restore local populations decimated by the effects of Dutch elm disease on native or archaeophytic elms. The Cheshire Wildlife Trust, for example, has planted 1,000 White Elms on its reserves in the former Vale Royal district of the county.^[5]

Notable trees

The three largest known trees in Europe are at Gülitz in Germany (3.1 m d.b.h.), at Komorów in Poland (2.96 m d.b.h. in 2011), known as the Witcher (tree), and at Bergemolo in Piedmont, Italy (bole-girth 6.2 m, height 26 m., 2008).^[18] Other veterans survive at Casteau, Belgium (bole-girth 5.15 m), in Rahnsdorf near Berlin (bole-girth 4.5 m)^[19] and in Ritvala, Finland (bole-girth 4.49 m).^[20] A lane of Ulmus laevis is found at Eibergen, Netherlands.

Ulmus laevis is occasionally planted as an ornamental tree in the UK. The UK Champion is at Ferry Farm, Harewood, Cornwall (27 m high, 1.8 m d.b.h.). Other examples are few and far between but sometimes of great age, surviving today amid diseased native elm near Torpoint.^[21] Others can be found in Edinburgh (East Fettes Avenue opposite Inverleith Allotments, North Merchiston Cemetery), London (Riverside Walk, near Royal Botanic Gardens, Kew, and at Peckham and Tooting), Brighton & Hove, and near St. Albans.

In the USA, a tree of 31.4 m (103 ft) in height grows at 3331 NE Hancock Street in Portland, Oregon; its age is not known.^[22]

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  U. laevis, Casteau, Belgium

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  U. laevis near the Red House, Česká Lípa, Czech Republic

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  Columnar form, Entraygues, France

Uses

The timber of the White Elm is of poor quality, the cross-grain causing problems when machined, and thus of little practical use to man, not even as firewood. The density of the timber is significantly lower than that of other European elms. However, owing to its rapid growth, tolerance of soil compaction, air pollution and de-icing salts, the tree has long been used for amenity planting in towns and along roadsides.^[23]

Propagation

Usually easy to grow from seed sown to a depth of 6 mm in ordinary compost and kept well-watered. However, as seed viability can vary greatly from year to year, softwood cuttings taken in June may be a more reliable method. The cuttings strike very quickly, well within a fortnight, rapidly producing a dense matrix of roots.

Subspecies and varieties

Several putative varieties have been identified. A variety celtidea from what is now the Ukraine was reported by Rogowicz in the middle of the 19th century, but no examples are known to survive. Another variety parvifolia has been reported from Serbia.^[24]

Forms

In Russia several ornamental forms are recognized: f. aureovariegata, f. argentovariegata, f. rubra, and f. tiliifolia.

Cultivars

Compared with the other European species of elm, U. laevis has received scant horticultural attention, there being only five recorded cultivars: Aureovariegata, Colorans, Ornata, Pendula, Punctata, Urticifolia.

A pyramidal form was reported in 1888 from the Fredericksfelde cemetery in Berlin by Bolle ^[25] A line of similar monopodial trees can be found (2015) on the island in the Truyère at Entraygues, France.

Hybrids

U. laevis does not hybridize naturally, in common with the American Elm U. americana to which it is closely related. However, in experiments at the Arnold Arboretum, it was successfully crossed with U. thomasii and U. pumila; no such crosses have ever been released to commerce.

Accessions

Europe

• Arboretum de La Petite Loiterie,^[26] Monthodon, France. No details available
• Arboretum Freiburg-Günterstal,^[27] Germany, no details available
• Brighton & Hove City Council, UK, NCCPG Elm Collection. Ten trees at Hove Recreation Ground, Hove.
• Copenhagen University, Botanic Garden. No details available.
• ELTE Botanic Garden Budapest. Acc. nos. 1998-0718, 1998-0719.
• Grange Farm Arboretum, Sutton St. James, Spalding, Lincolnshire, UK. Acc. no. 502.
• Great Fontley Butterfly Conservation Elm Trials plantation, UK. Two planted 2003, grown from cuttings of specimen at RBG Wakehurst Place. Acc. no. 1973-21048.
• Hortus Botanicus Nationalis, Salaspils, Latvia. Acc. nos. 18136, 18140.
• Linnaean Gardens of Uppsala, Sweden. Acc. no. 1930-1014.
• Royal Botanic Garden Edinburgh, UK. Acc. no. 20070643, from seed wild collected in Val d'Allier, France.
• Royal Botanic Gardens Kew, UK. Acc. nos. 1969-17302, 1973-11712.
• Royal Botanic Gardens, Wakehurst Place, UK. Acc. no. 1973-21048.
• Royal Horticultural Society Gardens, Wisley, UK. No details available.
• Sir Harold Hillier Gardens, UK. Acc. no. 1981-2446.
• Strona Arboretum Ulmus lamellosa, University of Life Sciences, Warsaw, Poland.
• Tallinn Botanic Garden, Estonia. No accession details available.
• Thenford House arboretum, Oxfordshire, UK. No details available.
• 'The Leys', University Parks, Oxford, UK. Acc. no. 02678.
• Westonbirt Arboretum,^[28] Tetbury, Glos., UK, planted 1997. Acc. no. 1995/322
• Wijdemeren City Council, Netherlands, Elm Collection. Planted 1990 Tjalk, Loosdrecht; 2007 Hinderdam, Nederhorst den Berg; elm lane De Kwakel, Kortenhoef in 2009.

North America

• Arnold Arboretum. Acc. nos. 17910, 637-79, 6951, 753-80.
• Brenton Arboretum, Dallas Center, Iowa. No details available.
• Brooklyn Botanic Garden,^[29] New York. Acc. no. X02589.
• Dominion Arboretum, Canada. No details available
• Longwood Gardens. Acc. nos. 1964-0568, 1964-1119.
• Morton Arboretum, Illinois. Acc. nos. 1302-27, 446-48, 492-64, 27-98.^[30]

Nurseries

• Arboretum Waasland,^[31] Nieuwkerken-Waas, Belgium.
• Boomkwekerij Oirschot,^[32] Oirschot, Netherlands
• Crown Nursery,^[33] Ufford, Suffolk, UK
• Dulford Nurseries,^[34] Cullompton, Devon, UK
• Landcare Tree Nursery,^[35] Old Sodbury, South Gloucestershire, UK
• Lorenz von Ehren,^[36] Hamburg, Germany
• Noordplant , Glimmen, Netherlands.
• UmbraFlor,^[37] Spello, Italy

References

External links

• Collin, E., 'Ulmus laevis: Technical Guidelines for Genetic Conservation and Use', euforgen.org (2003)
• Ecology of the European White Elm
• Ulmus laevis distribution map: linnaeus.nrm.se

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