As with other members of the Field Elm group, the taxonomy of Plot Elm has been a matter of contention, several authorities, notably Professor Clive A. Stace in New Flora of the British Isles (2010),[10][11][12] recognizing it as a species in its own right. It is as U. plotii Druce that the specimens held by the Royal Botanic Gardens at Kew and Wakehurst Place are listed. R. H. Richens, however, contended (1983) that it is simply one of the more distinctive clones of the polymorphous Ulmus minor, conjecturing that it arose as an U. minor sport and that its incidence in the English Midlands may have been linked to its use as a distinctive marker along Drovers' roads.[13]: 54 [14] After Richens had challenged the species hypothesis, the tree was the subject of a study at the Royal Botanic Garden Edinburgh by Dr Max Coleman (2000), which showed that trees a perfect fit with the 'type' material of Plot elm were of a single clone (genetically identical to each other).[15][16] 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, Coleman preferred the designation U. minor 'Plotii'[17] to U. minor var. plotii, a form used in late 20th-century publications.[18]
Alfred Rehder considered Ulmus Plotii Druce to be synonymous with Jonathan Stokes' Ulmus surculosa argutifolia which was located at Furnace Mill near North Wingfield, Derbyshire,[note 1] before 1812.[19][20][21] Earlier still, a herbarium specimen labelled Ulmus angustissima collected in the 1670s by Edward Morgan, the Welsh botanist referred to by Evelyn in his Diary and colleague of Thomas Johnson, was identified by Druce in 1919 as Ulmus plotii.[22] Morgan's source location is not recorded; the nearest Plot Elm (recorded in the 20th century) to his North Wales home was in Shropshire.[6][23][24][25]
^Stace, C. A. (1997). New Flora of the British Isles, 2nd edition. Cambridge University Press.
^Melville, R. (1978). "On the discrimination of species in hybrid swarms with special reference to Ulmus and the nomenclature of U. minor (Mill.) and U. carpinifolia (Gled.)". Taxon. 27 (4): 345–351. doi:10.2307/1220370. JSTOR1220370.
^Richens, R. H. (1983). Elm. Cambridge University Press. ISBN0521249163.
^Coleman, Max (2002). "British elms". British Wildlife. Vol. 13, no. 6. pp. 390–395.
^Kemp, Eddie (1979). "The Plantsman's Elm", in Clouston, Brian; Stansfield, Kathy (eds.), After the Elm; London: Heinemann; p.32
^Rehder, Alfred (1949). "Ulmaceae". Bibliography of cultivated trees and shrubs hardy in the cooler temperate regions of the Northern Hemisphere. Jamaica Plain, Mass., Arnold Arboretum of Harvard Univ. p. 143.
^White, J. & More, D. (2002). Trees of Britain & Northern Europe. Cassell's, London.
^Chatters, C. (2009) Flowers of the Forest – Plants and people of the New Forest National Park. Wildguides, Old Basing, England. ISBN978-1-903657-19-5
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