Ulmus minor 'Sarniensis'

The Field Elm cultivar Ulmus minor 'Sarniensis', known variously as Guernsey elm, Jersey elm, Wheatley elm, or Southampton elm, was first described by MacCulloch in 1815 from trees on Guernsey, and was planted in the Royal Horticultural Society's gardens in the 1820s. It was listed in the Loddiges catalogue of 1836 as Ulmus sarniensis and by Loudon in Hortus lignosus londinensis (1838) as U. campestris var. sarniensis. The origin of the tree remains obscure; Richens believed it "a mutant of a French population of Field elm", noting that "elms of similar leaf-form occur in Cotentin and in northern Brittany. They vary much in habit but some have a tendency to pyramidal growth. Whether the distinctive habit first developed on the mainland or in Guernsey is uncertain."

Melville, believing the cultivar a hybrid between Cornish elm U. minor 'Stricta' and Dutch elm Ulmus × hollandica, adopted the name U. × sarniensis (Loud.) Bancroft. Its clonal origin is (to date) suspected rather than proved, but the apparent uniformity of this taxon makes it likely to be a clone. A number of specimens in northern Britain were DNA-tested in 2013 by Forest Research, Roslin, Midlothian, and were found to be the same clone. Arguing in a 2002 paper that there was no clear distinction between species and subspecies, and suggesting that known or suspected clones of U. minor, once cultivated and named, should be treated as cultivars, Dr Max Coleman of Royal Botanic Garden Edinburgh preferred the designation U. minor 'Sarniensis'.

Guernsey elm was often misnamed 'Cornish elm' in the UK by the local authorities who planted it extensively.