Ulmus 'Nanguen'

Ulmus 'Nanguen' (selling name Lutèce) 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' × ('Bea Schwarz' selfed, clone 336[1]), an ancestry comprising four field elms (U. minor), a wych elm (U. glabra), the curious Exeter Elm ('Exoniensis'), and a frost-resistant selection of the Himalayan elm (U. wallichiana). [2]

Ulmus 'Nanguen'
Lutèce aged 20 years, Great Fontley, UK
GenusUlmus
Hybrid parentage'Plantyn' × ('Bea Schwarz' × 'Bea Schwarz' selfed)
Cultivar'Nanguen' = Lutece
OriginWageningen, The Netherlands

Originally identified as clone 812, Lutèce was not promoted by the Dutch owing to unfounded fears that it may prove susceptible to coral spot fungus (Nectria cinnabarina). Instead, 812 was acquired by the French Institut National de la Recherche Agronomique (INRA), which subjected the tree to 20 years of field trials in the Bois de Vincennes, Paris, before patenting and release in 2002 as 'Nanguen' = Lutèce.[3][4] Lutèce has been deemed the modern cultivar most closely resembling the native European elms.[5]

Unlicenced propagation of Lutèce is prohibited under Certificat d'Obtention Végétale (COV) EU 17197 until its expiry on 31 December 2036.

Description

The stem of Lutèce typically forks at a height of 1–2 m, where 3–5 steeply ascending branches develop in conjunction with more obtusely angled lower side branches to form an amorphous open crown. The ultimate size and shape of this cultivar remain unknown but, given its ancestry, it should make a large tree.[6] The trees planted in the Bois de Vincennes attained an average height of 12.5 m with a trunk diameter of 22 cm at 20 years of age.[7] Quick growing on moist, well-drained soils, increasing in height by an average of 80 cm per annum, the tree commences flowering in late March when aged seven years. The leaves are elliptic to orbicular < 11 cm long × 9 cm wide, the acuminate apex far less pronounced than in most other elms, with coarse, doubly serrate margins; the upper surface is rough. The leaves flush relatively late, rarely before mid-May in England. The samarae are obovate, slightly notched at the outer end, 14–22 mm long by 11–17 mm broad. The seed is not central but slightly nearer the notch, and ripens in late May.[2]

  • LUTECE in winter
    LUTECE in winter
  • Lutèce leaf in August
    Lutèce leaf in August
  • Lutèce samarae
    Lutèce samarae
  • White-letter Hairstreak on Lutèce, Sweden
    White-letter Hairstreak on Lutèce, Sweden
  • Lutèce, IoW, hosting White-letter Hairstreak
    Lutèce, IoW, hosting White-letter Hairstreak
  • Lutèce root suckering, Ports Down, UK
    Lutèce root suckering, Ports Down, UK
  • Bark of 22-year-old tree
    Bark of 22-year-old tree

Pests and diseases

Lutèce exhibited a high resistance to Dutch elm disease when inoculated with unnaturally high doses of the causal fungus Ophiostoma novo-ulmi, and was rated 5 out of 5 in Dutch tests.[8] Tests in France by INRA confirmed the tree has 'highly resistant'.[7][9] [10] Used as a control in IRSTEA's trials of French Ulmus minor clones, it was noted that not one specimen succumbed to natural infection by DED.[2]

Cultivation

The cultivar is now being widely planted in cities, notably Paris, and rural areas of France.[11] In trials in southern England, the tree has proven very hardy, tolerant of sea winds, summer droughts, and ground waterlogged during winter. However, top-growth can occasionally outpace root development, leaving some trees susceptible to wind-rock when young and necessitating staking for up to six years. Lutèce is cold hardy, and has survived winter temperatures as low as −30° C in Sweden.[2]

Lutèce was introduced to the UK by the Hampshire & Isle of Wight Branch, Butterfly Conservation, in 2001, as part of its assessment of DED-resistant cultivars as potential hosts of the endangered White-letter Hairstreak. The plants were donated by SAPHO (Syndicate for the improvement of ornamental horticultural plants) ahead of its release to commerce.[2] Two lines of ten Lutèce have been planted at Wrest Park, Bedfordshire.[12] Lutèce was introduced to North America in 2010, with the supply of two small specimens to the USDA, Washington, D.C., released from quarantine in 2013. Lutèce is not known to have been introduced to Australasia.

Increasing Lutèce by softwood cuttings is relatively straightforward, however these lose their viability as the donor trees mature. Several French nurseries resorted to grafting onto 'Sapporo Autumn Gold' rootstocks, but this practice ended in 2022. [2]

Natural hybridization

The flowering period of Lutèce coincides in part with that of field elm, and the seeds harvested have produced viable seedlings, though possibly selfed.[2]

Conservation role

Over 5000 Lutèce were planted on the Isle of Wight by Natural Enterprise, and in smaller numbers in Hampshire by Butterfly Conservation and the Forestry Commission, in the hope the tree would host the white-letter hairstreak butterfly (Satyrium w-album), a monophagic species which remains in serious decline as a consequence of Dutch elm disease. This was confirmed in 2015 with the discovery of the butterfly breeding on specimens planted in 2003 at Towngate, Newport, Isle of Wight (see photo 5 in Gallery) and at Great Fontley in 2021 .[2]

Etymology

The registered cultivar name 'Nanguen' is a contraction of Nancy and Wagueningen, the locations of the French and Dutch research institutes. The selling name Lutèce is the French derivation of Lutetia, the ancient Roman name for the settlement which later became Paris. The name was adopted in recognition of the trials of the cultivar conducted by INRA in the Bois de Vincennes.

Accessions

Europe

North America

Nurseries
Europe

References
  1. Tijdgat, M. (2020): Ulmus – Gebruikswaarde- en sortimentsonderzoek in de praktijk. Dendroflora Nr. 56-2020, pages 98-99. Koninklijke Vereniging voor Boskoopse Culturen & Nederlandse Dendrologische Vereniging
  2. Butterfly Conservation (2023). Disease-resistant elm cultivars , Butterfly Conservation, Lulworth, England.
  3. "Ulmus LUTECE® 'Nanguen'". Sapho.fr. Retrieved 29 March 2022.
  4. "Forest Health in France 2002" (PDF). Paris, France: Department of Forest Health.
  5. Hillier, J. G. & Lancaster, R. (Eds). (2014). The Hillier Manual of Trees and Shrubs, 8th revised edition. Royal Horticultural Society; London. ISBN 978-1907057472
  6. Johnson, H. (2010). Trees. London: Mitchell Beazley. ISBN 9781845330552
  7. Pinon, J. (July 2007). "Les ormes résistants à la graphiose" [Elms resistant to Dutch Elm Disease] (PDF). Forêt-entreprise. Paris, France: IDF (175): 37–41. ISSN 0752-5974. Retrieved 26 October 2017.
  8. 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
  9. Pinon, J., Lohou, C. & Cadic, A. (1998). Hybrid Elms (Ulmus Spp.): Adaptability in Paris and behaviour towards Dutch elm disease (Ophiostoma novo-ulmi). Acta Horticulturae 496, 107-114, 1998.
  10. "Lutece - Resistant Elms". Archived from the original on 2013-12-04. Retrieved 2013-08-12.
  11. "Lutèce®, a resistant variety brings elms back to Paris". All The News. Nantes, France: Institut national de la recherche agronomique (INRA). 15 April 2005. Archived from the original on 25 November 2006.
  12. Tim Richardson, 'Can we resurrect the English elm?', The Daily Telegraph, 6 March 2021
  13. "List of plants in the {elm} collection". Brighton & Hove City Council. Retrieved 23 September 2016.
  14. "Who are we ?". Sapho.fr. Retrieved 29 March 2022.

Pictures

Photographs of the Isle of Wight's Island 2000 Trust planting Lutece elms can be seen at the Flickr website here at Special Elm Trees and New Elms being planted out..

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