Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Believed to be originally native to Asia, the disease was accidentally introduced into America, Europe, and New Zealand. In these regions it has devastated native populations of elms that did not have resistance to the disease. The name "Dutch elm disease" refers to its identification in 1921 and later in the Netherlands by Dutch phytopathologists Bea Schwarz and Christine Buisman, who both worked with professor Johanna Westerdijk. The disease affects species in the genera Ulmus and Zelkova, therefore it is not specific to the Dutch elm hybrid.
Ulmus minor subsp. minor, the narrow-leaved elm, was the name used by R. H. Richens (1983) for English field elms that were not English elm, Cornish elm, Lock elm or Guernsey elm. Many publications, however, continue to use plain Ulmus minor for Richens's subspecies, a name Richens reserved for the undifferentiated continental field elms. Dr Max Coleman of Royal Botanic Garden Edinburgh argued in his 2002 paper 'British Elms' that there was no clear distinction between species and subspecies.
Ulmus 'San Zanobi' is a hybrid elm cultivar raised by the Istituto per la Protezione delle Piante (IPP) in Florence, from a crossing of the Dutch hybrid 'Plantyn' and the Siberian Elm Ulmus pumila clone 'S 15'; it was released to commerce in 2002. 'San Zanobi' was introduced to the UK in 2004 by Hampshire & Isle of Wight Branch, Butterfly Conservation, as part of its assessment of DED-resistant cultivars as potential hosts of the endangered White-letter Hairstreak.
Ulmus 'Plinio' is a hybrid elm cultivar derived from a crossing of the Dutch cultivar 'Plantyn' with the Siberian Elm Ulmus pumila clone 'S.2'. 'Plinio' was raised by the Istituto per la Protezione delle Piante (IPP), in Florence and released for sale in 2003. 'Plinio' was introduced to the UK in 2004 by Hampshire & Isle of Wight Branch, Butterfly Conservation, as part of its assessment of DED-resistant cultivars as potential hosts of the endangered White-letter Hairstreak.
Ulmus davidiana var. japonica, the Japanese elm, is one of the larger and more graceful Asiatic elms, endemic to much of continental northeast Asia and Japan, where it grows in swamp forest on young alluvial soils, although much of this habitat has now been lost to intensive rice cultivation.
Ulmus 'Nanguen' is a complex fourth generation Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. Lutèce was derived from the cross 'Plantyn' ×, an ancestry comprising four field elms, a wych elm, the curious Exeter Elm ('Exoniensis'), and a frost-resistant selection of the Himalayan elm.
Ulmus chenmouiW. C. Cheng, commonly known as the Chenmou, or Langya Mountain elm, is a small deciduous tree from the more temperate provinces of Anhui and Jiangsu in eastern China, where it is found at elevations below 200 m on the Langya Shan and Baohua Shan mountains. The tree was unknown in the West until 1979, when seeds were sent from Beijing to the De Dorschkamp research institute at Wageningen in the Netherlands.
Ulmus 'Plantyn' was one of three Dutch hybrid elms released by the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, in 1973. Derived from a crossing of the Dutch hybrids '202' and '302', it was to prove of great significance in later developments. A selfed seedling was to become the first Dutch clone to prove effectively immune to disease, released in 1989 as 'Columella'. 'Plantyn' was also destined to be the female parent of Lutèce released in 2002. In Italy, 'Plantyn' was used again as female parent in hybridizations with the Siberian Elm Ulmus pumila by the Istituto per la Protezione delle Piante (IPP), to create three new cultivars better adapted to the Mediterranean climate.
Ulmus 'Wanoux' is a Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, from an open pollination of 'Plantyn'. Originally identified as clone No. 762, it was selected for assessment by the French Institut National de la Recherche Agronomique (INRA), which patented it as 'Wanoux' in 2006.
Ulmus 'Columella' is a Dutch elm cultivar raised by the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. Originally thought to have been derived from a selfed or openly pollinated seedling of the hybrid clone 'Plantyn', DNA analysis later determined it arose from a cross of 'Plantyn' and Ulmus minor. Sown in 1967, it was released for sale in 1989 after proving extremely resistant to Dutch elm disease following injection with unnaturally high doses of the pathogen, Ophiostoma novo-ulmi. However, propagated by grafting onto wych elm rootstocks, graft failure owing to incompatibility has become a common occurrence in the Netherlands.
Ulmus 'Exoniensis', the Exeter elm, was discovered near Exeter, England, in 1826, and propagated by the Ford & Please nursery in that city. Traditionally believed to be a cultivar of the Wych Elm U. glabra, its fastigiate shape when young, upward-curving tracery, small samarae and leaves, late leaf-flush and late leaf-fall, taken with its south-west England provenance, suggest a link with the Cornish Elm, which shares these characteristics. The seed, however, is on the stalk side of the samara, a feature of wych elm and its cultivars, whereas in hybrids it would be displaced towards the notch.
The Field Elm cultivar Ulmus minor 'Christine Buisman' was the first cultivar released by the Dutch elm breeding programme, initiated in response to the less virulent form of Dutch elm disease (DED), Ophiostoma ulmi, which afflicted Europe's elms after the First World War. 'Christine Buisman' was selected from a batch of 390 seedlings grown from seed collected in the Parque de la Quinta de la Fuente del Berro, Madrid, by Mrs Van Eeghen, a friend of elm researcher Johanna Westerdijk, in 1929 and named for the elm disease researcher Christine Buisman. Originally identified as Ulmus foliacea, it was later treated as Ulmus × hollandica by Melville. However, more recent research in Belgium using DNA markers has reaffirmed 'Christine Buisman' as a clone of U. minor.
The Japanese elm cultivar Ulmus davidianavar.japonica 'Prospector' was originally treated as a cultivar of Wilson's elm U. wilsonianaSchneid., a species sunk as Ulmus davidiana var. japonica by Fu. A U.S. National Arboretum introduction, it was selected in 1975 from a batch of 1965 seedlings in Delaware, Ohio, and released without patent restrictions in 1990. 'Prospector' proved moderately successful in the US National Elm Trial, averaging a survival rate of 76% overall.
Ulmus 'Arno' is an Italian hybrid cultivar derived from a crossing of 'Plantyn' with the Siberian Elm Ulmus pumila clone S.2. It was raised by the Istituto per la Protezione delle Piante (IPP) in Florence, and released in 2007. However, 'Arno' was not a commercial success; propagation had ceased by 2010, and it is no longer patent protected.
Ulmus 'Fiorente' is a hybrid cultivar elm derived from a crossing of the Siberian Elm Ulmus pumila clone 'S.10' from Lucca, Italy, with the Ulmus minor clone 'C.02' from Lungarno, Florence, by the Istituto per la Protezione delle Piante (IPP), part of the Italian National Research Council, in Florence. The tree is protected by Plant Breeders' Rights bestowed by the EU on 25 March 2010.
Ulmus laciniata var. nikkoensisRehder, the Nikko elm, was discovered as a seedling near Lake Chūzenji, near Nikkō, Japan, and obtained by the Arnold Arboretum in 1905. The taxonomy of the tree remains a matter of contention, and has been considered possibly a hybrid of U. laciniata and U. davidiana var. japonica. However, in crossability experiments at the Arnold Arboretum in the 1970s, U. laciniata, a protogynous species, was found to be incompatible with U. davidiana var. japonica, which is protandrous.
Ulmus 'Morfeo' is a hybrid elm cultivar raised by the Istituto per la Protezione delle Piante (IPP), Florence, in 2000. 'Morfeo' arose from a crossing of the Dutch hybrid clone '405' and the Chenmou Elm, the latter a small tree from the provinces of Anhui and Jiangsu in eastern China, The '405' clone is a full sister of 'Groeneveld', a crossing of an English U. × hollandica and a French U. minor from the Barbier Nursery, Orléans.
The field elm cultivar Ulmus minor 'Ademuz' was cloned by root cuttings from a tree assumed to be growing in or near the eponymous town 100 km north-west of Valencia, Spain. The tree was discovered in 1996 by Margarita Burón of the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid (UPM). 'Ademuz' is one of a number of U. minor clones found to have a very high resistance to Dutch Elm Disease, on a par with, if not greater than, the hybrid cultivar 'Sapporo Autumn Gold' grown as a control. In the Madrid study, the appearance of the tree was rated 4.5 / 5, the most attractive of the seven selected cultivars.
The field elm cultivar Ulmus minor 'Dehesa de Amaniel' was raised from seed collected in 1999 from a tree growing in the Dehesa de la Villa park, within the Moncloa-Aravaca district of north-west Madrid by researchers at the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid. 'Dehesa de Amaniel' is one of a number of Spanish Ulmus minor found to have a very high resistance to Dutch Elm Disease, on a par with, if not greater than, the hybrid cultivar 'Sapporo Autumn Gold'.
The Field Elm cultivar Ulmus minor 'Dehesa de la Villa' was cloned by root cuttings from a tree growing in the eponymous park within the Moncloa-Aravaca district of north-west Madrid, by researchers at the Escuela Técnica Superior de Ingenieros de Montes, Universidad Politėcnica de Madrid in 1990.
