Ulmus 'Nanguen'

''Ulmus'' 'Nanguen' (selling name ) is a complex fourth generation Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. was derived from the cross 'Plantyn' × ( 'Bea Schwarz' selfed), 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''). Butterfly Conservation (2023). ''Disease-resistant elm cultivars'

Butterfly Conservation, Lulworth, England.

Originally identified as clone 812, 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' = .
has been deemed the modern cultivar most closely resembling the native European elms.Hillier, J. G. & Lancaster, R. (Eds). (2014). ''The Hillier Manual of Trees and Shrubs'', 8th revised edition. Royal Horticultural Society; London.

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

Description

The stem of 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.Johnson, H. (2010). ''Trees''. London: Mitchell Beazley. 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.
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.

File:LUTECE in winter.jpg, LUTECE in winter
File:Lutece leaf 2.jpg, leaf in August
File:Ulmus LUTECE samarae.jpg, samarae
File:WLH Julita.JPG, White-letter Hairstreak on , Sweden
File:LUTECE Towngate Newport 2.jpg, , IoW, hosting White-letter Hairstreak
File:LUTECE suckering, Nelson Reservoir 3 (2).jpg, root suckering, Ports Down, UK
File:Bark of Dutch hybrid elm Ulmus 'Nanguen' = LUTECE.jpg, Bark of 22-year-old tree

Pests and diseases

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.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. Tests in France by INRA confirmed the tree has 'highly resistant'.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. In trials conducted by the Istituto per la Protezione delle Piante, Florence, suffered 19.8% defoliation and 11.7% dieback when inoculated, compared with 2.8% and 1.2% resp. for 'Sapporo Autumn Gold', and 50% and 35.5% resp. for 'Lobel'.Santini, A, et al. (2002). 'San Zanobi' and 'Plinio' Elm trees. ''HortScience'' 37(7): 1139–1141, 2002. 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.

The presence of ''U. wallichiana'' in the ancestry of poses the risk of susceptibility to elm yellows (phloem necrosis, not known in the UK), which seriously damaged its Dutch stablemate 'Lobel' used as a control in the Italian elm breeding programme.Mittempergher, L., (2000). Elm Yellows in Europe. In: ''The Elms, Conservation and Disease Management.'' 103–119. Dunn C.P., ed. Kluwer Academic Press Publishers, Boston, USA.

Cultivation

The cultivar is now being widely planted in cities, notably Paris, and rural areas of France. 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 often outpace root development, leaving some trees susceptible to wind-rock when young and necessitating staking for up to six years. is cold hardy, and has survived winter temperatures as low as −30° C in Sweden.

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. Two lines of ten have been planted at Wrest Park, Bedfordshire.Tim Richardson, 'Can we resurrect the English elm?', ''The Daily Telegraph'', 6 March 2021
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. is not known to have been introduced to Australasia.

Increasing by softwood cuttings is relatively straightforward, however these lose their viability as the trees mature, and French nurseries now resort to grafting onto 'Sapporo Autumn Gold' rootstocks. As the latter does not sucker from roots, the practice eliminates natural vegetative regeneration

Natural hybridization

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

Conservation role

Over 5000 were planted on the Isle of Wight b
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).

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 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

*Brighton & Hove City Council, UK. NCCPG Elm Collection. Stanmer Nursery.
*Grange Farm Arboretum, Sutton St James, Spalding, Lincolnshire, UK. Acc. no. not known.
*Great Fontley Farm, Fareham, UK. ''Butterfly Conservation'' Elm Trials plantation, Home Field and the Platt, five small whips donated by SAPHO in 2002.
*Longstock Parkbr>Leckford Estate, Hampshire , Farm Produce , The Waitrose Farm
Arboretum, UK. One juvenile specimen planted 2010.
* Royal Botanic Garden Edinburgh, UK. Acc. no. 20042084
*Sir Harold Hillier Gardens, UK. Acc. no. 2004.0515
*Wijdemeren City Council, Netherlands. Elm collection. Used in elm trials Ankeveen 2009.

North America

* National Arboretum, Washington, D.C., US. Two small trees imported in 2010.

Nurseries

;Europe
*Batouwe Boomkwekerijen B.V
Batouwe boomkwekerijen BV
Dodewaard, Netherlands. Potted whips.
*F P Matthews 'Trees for Life
Ulmus LUTECE ('Nanguen')
Tenbury Wells, Worcestershire, UK. Potted trees, not grafted, propagated under licence.
*Les Pépiniéres Minie

(UK: [e-mail]), Beaufort-en-Vallée

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