Ulmus 'New Horizon'
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| Ulmus hybrid |
|---|
 'New Horizon', Great Fontley, UK |
| Hybrid parentage |
| Ulmus pumila × U. davidiana var. japonica |
| Cultivar |
| 'New Horizon' |
| Origin |
| WARF, Wisconsin, USA |
An American cultivar raised by the Wisconsin Alumni Research Foundation (WARF), 'New Horizon' was derived from a crossing of Siberian Elm Ulmus pumila with Japanese Elm Ulmus davidiana var. japonica [1]. The tree was patented in 1994, and is now also grown under licence by the Conrad Appel nursery in Darmstadt, Germany, where it forms one of the hybrid elms offered in the Resista series [1]. It has become a popular choice as a street tree courtesy of its compact habit and high resistance to Dutch elm disease, elm leaf miner, and verticillium wilt [2]. 80 trees were donated to the Greater London Council as part of the grower's European Elm City promotion in 2004; similar gifts were also made to Belfast, Cardiff, and Hamburg [3].
Unlike an earlier crossing of the same species 'Sapporo Autumn Gold', the tree has a compact vase-shaped form, with comparatively dense foliage comprising elliptical leaves <10 cm long.
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 [4]. In the Netherlands, removal of sideshoots from the lower trunk was found to be necessary twice a year. In trials in eastern Arizona [2] 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 Trial [3] coordinated by Colorado State University.
In England an assessment by Butterfly Conservation found its growth on heavy, poorly-drained ground negligible. Moreover, trees at exposed sites exhibited much the same degree of dieback experienced in the Arizona trials despite the extreme differences in climate. However no losses were 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 [5].
Contents |
[edit] Arboreta etc. accessions
[edit] North America
- Bickelhaupt Arboretum, Clinton, Iowa, acc. no. 01-008
- Chicago Botanic Garden, Glencoe, Illinois. 3 trees, no other details available.
[edit] Europe
- Arboretum de La Petite Loiterie [4], Monthodon, France. No details available.
- Botanischer Garten Marburg [5], Marburg, Germany. No details available.
- Brighton & Hove City Council, NCCPG Elm Collection [6], UK.
- Great Fontley Farm, Fareham, UK, Butterfly Conservation elm trials plantation, Home Field K4, planted 2007.
- Royal Horticultural Society Gardens, Wisley, UK, no details available.
- Sir Harold Hillier Gardens, UK acc. no. 2004.0177
[edit] Nurseries
[edit] North America
- Charles J. Fiore Nursery [7], Prairie View, Illinois.
- J. Frank Schmidt & Son [8], Boring, Oregon.
- Johnson's Nursery [9], Menomonee Falls, Wisconsin
[edit] Europe
- Bonte Hoek kwekerijen [10], Glimmen, Netherlands.
- Conrad Appel, Darmstadt, Germany.
- Eisele GmbH & Co KG Darmstadt, Germany.
- Hilliers Nurseries [11], UK.
[edit] References
- ^ Santamour, F. S., & Bentz, S. E. Updated checklist of elm (Ulmus) cultivars for use in North America. Journal of Arboriculture, 21(3): May, 1995.
- ^ Pinon, J. (2007). Les ormes résistants à la graphiose. Forêt-entreprise, No. 175 - Juillet 2007, p 37-41, France.
- ^ Horticulture Week, Haymarket Publishing, London, UK, 24th April 2004.
- ^ Giblin, C. P. & Gillman, J. H. (2006). Elms for the Twin Cities: A Guide for Selection and Maintenance. University of Minnesota.
- ^ Brookes, A. H. (2006). An evaluation of disease-resistant hybrid and exotic elms as larval host plants for the White-letter Hairstreak, Satyrium w-album. Part 1. Butterfly Conservation, Lulworth, England.
