and a very high level of leaf scorch in summer. The tree is currently being evaluated in the National Elm Trial 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 series ; 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 Germany . 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. 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), and Hamburg (the central City Park). In 2010, 100 trees were planted in the London borough of 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. Forty have been planted in Richmond Park, near the Dysart gate. 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. 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 Loiterie , Monthodon, France. No details available. Botanischer Garten Marburg , Marburg, Germany. No details available. Brighton & Hove City Council, UK. NCCPG Elm Collection. Planted frequently as a street tree.