Ulmus minor

Ulmus minor Mill., the Field Elm, is by far the most polymorphic of the European species, although its taxonomy remains a matter of contention. Its natural range is predominantly south European, extending to Asia Minor; its northern outposts are the Baltic islands of Öland and Gotland,^[1] although it may have been introduced here by man. The tree's typical habitat is low-lying forest along the main rivers, growing in association with oak and ash, where it tolerates summer floods as well as droughts.^[2]

Current treatment of the species owes much to Richens,^[3] who sank a number of British elms as either subspecies or varieties in 1968. However, Melville,^[4] writing 10 years later, identified five distinct species, several varieties and numerous complex hybrids. In 1992, 14 years after Melville, Armstrong ^[5] identified no fewer than 40 species and microspecies. Stace (1997) wrote of the British elms "The 2-species (glabra and minor) concept of Richens is not sufficiently discriminating to be of taxonomic value". Nevertheless, it is Richens’ classification which has been the most commonly adopted in recent years, although it is not used in Flora Europaea .^[6]

In 2009 Dr Max Coleman of the Royal Botanic Garden, Edinburgh wrote: "The advent of DNA fingerprinting has shed considerable light on the question. A number of studies have now shown that the distinctive forms Melville elevated to species and Richens lumped together as field elm are single clones, all genetically identical, which have been propagated by vegetative means such as cuttings or root suckers. This means that enigmatic British elms such as Plot's Elm and English Elm have been shown to be single clones of Field Elm. Although Richens did not have the evidence to prove it, he was correct in recognising a series of clones and grouping them together as a variable species." ^[7]

It is hoped that analysis of molecular markers will ultimately eliminate the taxonomic confusion.

Description

The tree typically grows to < 30 m and bears a rounded crown.^[8] The bark of the trunk is rough, furrowed lightly in older trees to form a block pattern. Young branchlets occasionally have corky wings. The shoots are slender compared with those of wych elm. The leaves are smaller than those of the other European species, hence the specific epithet minor, however they can vary greatly according to the maturity of the tree. Leaves on juvenile growth (suckers, seedlings etc.) are coarse and pubescent, whereas those on mature growth are generally smooth, though remaining highly variable in form; there are generally fewer than 12 pairs of side veins. A common characteristic is the presence of minute black glands along the leaf veins, detectable with the aid of a magnifying glass.^[2] The samarae are typically ovate and notched, the notch extending to the central seed.

The species readily produces suckers from roots and stumps, even after devastation by Dutch elm disease; consequently genetic resources are not considered endangered [http://www.ipgri.cgiar.org/Networks/euforgen/Networks/Scattered_Broadleaves/NHStrategies/UlmusSppConsStrategy.htm.].

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  U. minor foliage

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  Leaf and 1 Euro coin

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  Root-suckers spreading around a Field Elm

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  Ulmus minor - MHNT

Pests and diseases

Most trees are very susceptible to Dutch elm disease, including all the fashionable pre-20th century plantsman's clones (see Subspecies and varieties). However, Field Elm is genetically highly variable, and in 2013 researchers at the Universidad Politėcnica de Madrid announced the discovery and cloning of seven trees in Spain with levels of resistance greater than 'Sapporo Autumn Gold' ^[9] (see Cultivation).

Cultivation

Owing to its susceptibility to Dutch elm disease, U. minor is now uncommon in cultivation. However, in an ongoing project that began in the 1990s, several thousand surviving Field Elms have been tested for innate resistance by national research institutes in the EU, with a view to returning Field Elm to cultivation.^[10] Results from Spain (2013), for example, confirm that a very small number of surviving Field Elms (about 0.5% of those tested) appear to have comparatively high levels of tolerance of the disease, and it is hoped that a controlled crossing of the best of these will produce resistant Ulmus minor hybrids for cultivation.^[11]

In the UK, despite its late leaf-flush in the north and its suckering habits, continental Ulmus minor was occasionally planted as an ornamental urban tree. Augustine Henry wrote in 1913 that the U. minor planted in parks in Scotland were of French origin.^[12] Among mature survivors in Edinburgh (2013), the specimen in the grounds of Holyrood Palace, opposite Abbeyhill Crescent, the elm at the corner of Granton Road and Boswall Road in the forecourt of the former Royal Forth Yacht Club, and the elm on the corner of Abbey Mount and Regent Road, appear old enough to fall into this category.

Notable trees

Ulmus minor can live to a great age. An ancient Field Elm stood until recently in the village square of Metaxades, Thrace, Greece. Having abandoned their original village in 1286 after cholera outbreaks, the villagers re-founded it in the hills where a young elm was growing beside a spring. An elm (reputedly the original) and the fountain were the focal-point of the village until the late 20th century.^[13] A tree said to be of similar age (200 cm d.b.h.) still stands (2013) in the city of Sliven, Bulgaria; other veterans are said to survive in the village of Samuilovo, 7 km from Sliven.^[14][15][16] A tree reputedly over 650 years old survived in the centre of Biscarrosse south of Bordeaux until the summer of 2010, when it finally succumbed to Dutch elm disease.^[17] Another veteran with a 6-metre girth survives at Bettange, France, close to the Belgian border, reputedly planted in 1593.^[18] A tree approximately 400 years old and 5.55 metres in girth grows in the town of Mergozzo in Piedmont, Italy. 'L'olmo di Mergozzo', like its French counterparts 'l'orme de Biscarosse' and 'l’orme de Bettange', is hollowed out by age, its life prolonged by lopping. Another hollow veteran is the elm in the Plaza del Olmo in Navajas, Valencia, 6.3 metres in girth, planted in 1636 and featuring on the town crest.^[19]

The tallest recorded Field Elms in Greece were two specimens planted in 1650 beside the newly built church of the Archangels Michael and Gabriel, in Omali Voiou (Oμαλή Bοΐου) near Siatista, which, despite being open-grown trees, attained a height of 40 metres by the mid-20th century.^[20] The immemorial elm opposite the village square of Aidona in Thessaly, Greece ^[21] which has been "listed" as a national "Monument of Nature",^[22] lost its crown in a recent storm (2009) and has now been pollarded; it is regenerating vigorously. A rare example of a centuries-old Field Elm that retains its heartwood and crown is the 360-year old specimen in the village square of Strinylas, Corfu.^[23][24][25]

Cultivars

Numerous cultivars have been raised in Europe since the 18th century although, with the exception of the new Spanish trees, most are now probably extinct owing to the ravages of Dutch elm disease:

• Ademuz, Albo-Dentata, Amplifolia, Biltii, Concavaefolia, Cucullata, Dehesa de Amaniel, Dehesa de la Villa, Dijkwel, Erecta, Folia Alba-Punctata, Fuente Umbria, Hoersholmiensis, Holmstruph, Hunnybunii, Koopmannii, Laciniata, Lanuginosa, Latifolia, Majadahonda, Microphylla Purpurea, Microphylla Rubra, Pendula, Picturata, Propendens, Purpurascens, Retiro, Reverti, Rueppellii, Schuurhoek, Silvery Gem, Sowerbyi, Toledo, Tortuosa, Umbraculifera, Umbraculifera Gracilis, Variegata, Virgata

Hybrids

The tree's natural range generously overlaps that of Wych Elm Ulmus glabra to the north, and readily hybridizes with it to produce the so-called 'Dutch Elm' Ulmus × hollandica.

In Spain Ulmus minor has naturally hybridized with Siberian Elm U. pumila, which was introduced in the 16th century and which has spread widely since then, contributing to conservation concerns for the former species.^[26] The resulting hybrid has not yet been given a formal botanical name, though there are cultivated forms such as 'Recerta' and 'Fiorente' (see Hybrid cultivars).

• Ulmus × hollandica
• U. minor × U. pumila

Hybrid cultivars

The tree has featured strongly in artificial hybridization experiments in Europe and to a lesser extent in the USA. Most of the European research was based at Wageningen in the Netherlands until 1992, whence a number of hybrid cultivars have been commercially released since 1960. 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.^[27]

• Alba, Angustifolia, Arno, Aurea, Belgica (Belgian Elm), Cinerea, Clusius, Columella, Commelin, Dampieri, Dauvessei, Daveyi (Davey Elm), Den Haag, Dumont, Eleganto-Variegata, Fiorente, Fjerrestad, Frontier, Fulva, Gaujardii, Groeneveld, Haarlemensis, Hillieri, Homestead, Lobel, Major (Dutch Elm), Macrophylla Aurea, Marginata, Microphylla, Modiolina, Muscaviensis, Nanguen (LUTECE), Pioneer, Plantyn, Plinio, Pulverulenta, Recerta, San Zanobi, Scampstoniensis, Serpentina, Smithii (Downton Elm), Superba, Tricolor, Urban, Vegeta (Huntingdon Elm), Vegeta (Chichester Elm), Virens (Kidbrook Elm), Viscosa, Warnoux (VADA), Wredei (Golden Elm), Ypreau.

Subspecies and varieties

• Ulmus minor subsp. angustifolia - Cornish Elm
• Ulmus minor subsp. minor - Smooth-leaved Elm, Narrow-leaved Elm
• Ulmus minor var. plotii - Plot's Elm, Lock Elm
• Ulmus minor subsp. sarniensis - Guernsey Elm, Jersey Elm, Southampton Elm, Wheatley Elm

The name Ulmus minor subsp. minor was used by R. H. Richens ^[28] for Field Elm that was not English Elm, Cornish Elm, Lock Elm or Guernsey Elm. Many publications, however, continue to use plain Ulmus minor for Richens's Ulmus minor subsp. minor. Richens noted in 1983 that other varieties of Field Elm are distinguishable on the European mainland. Of these, he listed the small-leaved U. minor of France and Spain; the narrow-leaved U. minor of northern and central Italy; the densely-hairy leaved U. minor of southern Italy and Greece; the U. minor with small-toothed leaves from the Balkans; the U. minor with large-toothed leaves from the Danube region; and the small-leaved U. minor from southern Russia and the Ukraine.^[29] As for the English varieties, "the continental populations most closely related are in central Europe".^[30] He concluded, however, that owing to incomplete field-research at the time of writing [1983], it was "not possible to present an overall breakdown of the European Field Elm into regional varieties".^[31]

A form of U. minor not uncommon in central Europe, and considered sufficiently distinct by some continental botanists to be recognised as a variety, is the so-called korkulme (Germany), korkelm (Denmark), or wiąz korkowa (Poland) - U. minor var. suberosa ((Moench) Rehder), the 'Cork-barked elm' of A. Henry, who says it "appears to be a common variety in the forests of central Europe".^[32] Elwes and Henry, having seen specimens in Slavonia, Croatia, and in Gisselfelde, Denmark, as well as at Kew, describe it as having "branchlets of the second to the tenth year furnished with corky wings", but with "leaves and samarae as in the type". W. J. Bean reports it "to be often rather dwarf and to occur in dry habitats".^[33] A fine specimen so labelled, with thick corky branchlets giving a dense winter silhouette, stands in the Botanic Gardens of Visby in Gotland, Sweden,^[34] and others are found in the University of Copenhagen Arboretum ^[35] and in the Alexandru Buia Botanic Garden in the University of Craiova, Rumania.^[36][37][38] R. H. Richens, however, regarded the tree as undifferentiated U. minor, not distinct enough to merit varietal status, and the name a relic of taxonomic conservatism.^[39]

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  "U. minor var. suberosa" Kamień Pomorski, Poland

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  "U. minor var. suberosa" Branchlet, Białowieża forest, Poland

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  "U. minor var. suberosa" Białowieża forest, Poland

Accessions

North America

• U S National Arboretum , Washington, D.C., USA. Acc. nos. 12852, 64382.

Europe

• Arboretum de La Petite Loiterie , Monthodon, France. No details available
• Cambridge Botanic Garden , University of Cambridge, UK. No accession details available.
• Dubrava Arboretum, Lithuania. No details available.
• Linnaean Gardens of Uppsala, Finland. Acc. no. 1930-1013.
• Royal Botanic Garden Edinburgh, UK. Acc. nos. 19699368, 16899359, 19699365
• Sir Harold Hillier Gardens, UK. Acc. no. 2001-0188, 3 specimens collected in Iran, 2000.
• Strona Arboretum, University of Life Sciences, Warsaw, Poland.

Australasia

• Eastwoodhill Arboretum , Gisborne, New Zealand. 2 trees, details not known.

Nurseries

North America

None known

Europe

• Eggleston Hall Gardens , Eggleston, Barnard Castle, County Durham, UK
• Firecrest Tree & Shrub Nursery , Woodbridge, Suffolk, UK
• Lorenz von Ehren , Hamburg, Germany
• Trees & Hedges , Heathfield, East Sussex, UK
• UmbraFlor , Spello, Italy

External links

• Ulmus minor distribution map: linnaeus.nrm.se

References

Wikimedia Commons has media related to Field Elm.