New Horizon (elm Hybrid)

''Ulmus'' 'New Horizon' is an American hybrid cultivar raised by the Wisconsin Alumni Research Foundation (WARF), from a crossing of the Japanese Elm clone W43-8 = 'Reseda' (female parent) with Siberian Elm clone W426 grown from seed collected from a street tree at Yankton, South Dakota. Tested in the US National Elm Trial coordinated by Colorado State University

'New Horizon' averaged a survival rate of 74% after 10 years.'New Horizon' was patented in the US in 1994, while in Europe, it is marketed as one of the 'Resista' elm

protected under EU Plant breeders' rights, breeders' rights (EU council decision 2100/94).

Description

Unlike its elder stablemate 'Sapporo Autumn Gold', 'New Horizon' initially has a compact, pyramidal form, with comparatively dense foliage comprising glabrous, dark-green, elliptical leaves < 12 cm long by 7 cm broad, occasionally without the asymmetric bases typical of the genus. The perfect, apetalous wind-pollinated flowers appear in March, followed by the seeds in April; flowering, and consequent fruiting, is sparse, in common with its female parent Japanese Elm, and usually begins when the tree is aged 8 years.Smalley, E. & Guries, R. (1993). Patent application: Elm tree named New Horizon. US PP8684 P. U S Patent Office

/ref>

The tree's growth habit is unusual; in an assessment at U C Davis as part of the National Elm Trial, its stem diameter increased faster than any other of the 15 cultivars, but increase in height, averaging 0.9 m per annum, made it one of the slowest growing, vertically.

In commerce in the US, the tree is occasionally propagated by grafting onto an ''Ulmus pumila'' rootstock, rather than simply rooting cuttings as normally practiced in North America and Europe.

Image: New Horizon leaf with Euro.jpg, Leaf, with 1 Euro coin
Image: Ulmus New Horizon (Quai Sainte Marie Chal.jpg, 'New Horizon', Chalons-sur-Saône
Image: New Horizon trunk nobbles.jpg, Nobbled stem arising from regular pruning
Image: RN Ulmus New Horizon Groningen 2.JPG, 'New Horizon' Groningen, NL
Image: Ulmus 'New Horizon' bark.jpg, 'New Horizon' bark

Pests and diseases

'New Horizon' has a very high resistance to Dutch elm disease, rated 5 out of 5 in Europe;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. it is also resistant to elm leaf miner, and verticillium wilt. However, it has proven susceptible to attack by elm leaf beetle '' Xanthogaleruca luteola'' McPherson, G. et al. (2008). National elm trial: Initial report from Northern California. ''Western Arborist'', Fall 2009, 32–36.
and Japanese Beetle in the United States.Brady, C., Condra, J., & Potter, D. (2008) Resistance of Landscape-suitable Elm (Ulmus spp.) Cultivars to Japanese Beetle, Leaf Miners, and Gall Makers. ''2008 Research Report, Nursery & Landscape Program'', 15–16. University of Kentucky. Up until its patenting in 1993, no Coral Spot fungus infection had been observed in the US.

Cultivation

The tree has not been an unqualified success. In the elm trials conducted by the University of Minnesota, 'New Horizon' was found to need relatively high levels of maintenance, largely owing to its predilection for co-dominant leaders and heavy side branches.Giblin, C. P. & Gillman, J. H. (2006). ''Elms for the Twin Cities: A Guide for Selection and Maintenance.'' University of Minnesota. In the Netherlands, removal of sideshoots from the lower trunk was found to be necessary twice a year. In trials in eastern Arizonabr>
it often exhibited > 25% crown dieback over winter and a very high level of leaf scorch in summer. The tree is currently being evaluated in the National Elm Trialbr>
coordinated by Colorado State University.

'New Horizon' was introduced to Europe by the Conrad Appel nursery (ceased trading 2005) in Darmstadt, Germany, which propagated the tree under licence as one of the hybrid elms offered in the serie

the tree is currently propagated by Eisele GmbH. The tree was introduced to the UK and Ireland by Hillier Nurseries, who have sole distribution rights. 'New Horizon' was named 'Best New Plant Variety' by Horticulture Week in 2005, however, an assessment by ''Butterfly Conservation'' found its growth on heavy, poorly drained ground negligible. Nevertheless, the tree has tolerated flooding, by both freshwater in England, and seawater along the Baltic coast in German

Trees at exposed sites in Hampshire exhibited much the same degree of dieback experienced in the Arizona trials despite the extreme differences in climate. However no losses have been sustained, and in sheltered conditions on deep loam over chalk, 'New Horizon' grew healthily if relatively slowly, increasing in height by approximately 50 cm per annum, less than half the speed of the Dutch hybrids such as 'Dodoens' planted with it. The trees in the English trials first flowered aged 10 years, in late March. Butterfly Conservation (2023). ''Disease-resistant elm cultivars'

Butterfly Conservation, Lulworth, England.

In 2004, 80 trees were donated to the Greater London Council as part of the grower's European Elm City promotion; similar gifts were also made to Belfast, Cardiff (Pontcanna Fields, 100 trees planted in 2004),''Ulmus'' 'New Horizon', Pontcanna Fields, Cardiff; conservationfoundation.co.uk
/ref> and Hamburg (the central City Park).''Horticulture Week'', Haymarket Publishing, London, UK, 24 April 2004Gordon Mackenthun: 'Elms, Dutch Elm Disease and the Hamburg Elm Program

/ref> In 2010, 100 trees were planted in the London borough of Municipal Borough of Enfield, Enfield to aid and abet the conservation of the White-letter Hairstreak ''Satyrium w-album''

Another hundred were included in the tree planting at the Olympic Park, London, Olympic Park.McEwan, G. (2010). Great British Elm Experiment: nurseries and tree managers work to re-establish trees resistant to Dutch elm disease. ''Horticulture Week'', 9 April 2010, London. Forty have been planted in Richmond Park, near the Dysart gate.

File:Path through Pontcanna Fields - geograph.org.uk - 2244569.jpg, Winter 'New Horizon' avenue, Pontcanna Fields, Cardiff (2011)
File:Tree-lined path through Pontcanna Fields, Cardiff - geograph.org.uk - 3057387.jpg, Avenue of 'New Horizon', Pontcanna Fields, Cardiff (2012)
File:Misty morning, Pontcanna Fields, Cardiff (30625237095).jpg, 'New Horizon' avenue in mist, Pontcanna Fields, Cardiff (2016)

Conservation

'New Horizon' was found hosting the endangered White-letter Hairstreak at the Vauxhall Pleasure Gardens, London, in 2017; this is the first recorded instance of the butterfly breeding on the cultivar in the UK.Brookes, A. H. (2022). ''Great Fontley Elm Trial, 2022 Report''. Butterfly Conservation, Lulworth, England.

Accessions

North America

*Bickelhaupt Arboretum, US. Acc. no. 01–008
* Chicago Botanic Garden, US. 3 trees, no other details available.
* Morton Arboretum, US. Acc. no. 271–2008.

Europe

* Arboretum de la Petite Loiteriebr>
Monthodon, France. No details available.
*Botanischer Garten Marbur

Marburg, Germany. No details available.
*Brighton & Hove City Council, UK. NCCPG Elm Collection. Planted frequently as a street tree.
* Grange Farm Arboretum, Sutton St James, Spalding, Lincolnshire, UK. Acc. no. not known.
*Great Fontley Farm, Fareham, UK. ''Butterfly Conservation'' elm trials plantation, one standard planted 2007.
* Royal Botanic Gardens, Kew, UK. Acc. no. not known.
* Royal Horticultural Society Gardens, Wisley, UK. No details available.
*Sir Harold Hillier Gardens, Romsey, UK. Acc. no. 2004.0177

Nurseries

North America

*Carlton Plants, LL

Dayton, Oregon, US.
*Charles J. Fiore Nurser

Prairie View, Illinois, US.
*J. Frank Schmidt & So

Boring, Oregon, US.
*Johnson's Nurser

Menomonee Falls, Wisconsin, US.

Europe

*Arbor Boomkwekerijen n

Belgium.
*Clasen & Co Baumschulen GmbH, Rellingen, D-Rellingen, Germany.
*Eisele GmbH

Darmstadt, Germany.
*Hillier Nurserie

Ampfield, Hampshire, UK.
*Noordplan

Glimmen, Netherlands.
*Van Den Berk (UK) Ltd.

London, UK
*Vicq Arbor pépinières S

Vicq, Nord, Vicq, France.

References

{{Elm species, varieties, hybrids, hybrid cultivars and species cultivars , state=collapsed

Hybrid elm cultivar
Ulmus articles with images
Ulmus