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. In the
Netherlands, removal of sideshoots from the lower trunk was found to be necessary twice a year. In trials in eastern
Arizona 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 [https://web.archive.org/web/20080226012323/http://treehealth.agsci.colostate.edu/research/nationalelmtrial/NET_Cultivars.htm 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 trees were originally propagated by grafting, but this practice proved unsuccessful owing incompatibility with the rootstock; 50 trees planted in
Pau had to be replaced. 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 [https://translate.google.com/translate?hl=en&sl=de&u=http://www.resista-ulmen.com/static_website/de/de_6.htm&ei=iFhZTJ3zMKK80gTQktHmCA&sa=X&oi=translate&ct=result&resnum=3&ved=0CA8Q7gEwAg&prev=/search%3Fq%3Darshadi%2Bhillier%26hl%3Den%26sa%3DG. 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. Three, planted in 2014 as part of a resistant elms trial, stand by
the Isis in
Christ Church Meadow, Oxford. In 2020, a stand of 20 were planted at the National Memorial Arboretum in Alrewas, Staffordshire. File:Path through Pontcanna Fields - geograph.org.uk - 2244569.jpg|Winter 'New Horizon' avenue, Pontcanna Fields, Cardiff (2011) File:Wilhelminaplein Naaldwijk 2019.jpg|'New Horizon' and
'Rebona' alternating in the Wilhelminaplein,
Naaldwijk (2019) File:Elm Trees, Queen Victoria Street 2024-10-23.jpg|Line of 'New Horizon', Queen Victoria Street, London (2024) ==Conservation==