In trials in eastern Arizona , 'Frontier' and another American hybrid, 'Regal', were found to have the highest tolerance of the hot and arid climate, notably exhibiting minimal leaf scorch.
'Frontier' has had a limited introduction to Europe,[REF] where it is largely restricted to arboreta and elm collections; it also featured in trials in New Zealand during the 1990s at the Hortresearch station, Palmerston North.