Editing Elm (section)

== Taxonomy ==
{{main|List of elm species|List of elm cultivars, hybrids and hybrid cultivars|List of elm synonyms and accepted names}}

There are about 30 to 40 [[species]] of ''Ulmus''; the ambiguity in number results from difficulty in delineating species, owing to the ease of [[Hybrid (biology)|hybridization]] between them and the development of local seed-sterile vegetatively propagated [[Theory of species|microspecies]] in some areas, mainly in the Ulmus field elm (''[[Ulmus minor]]'') group. [[Oliver Rackham]]<ref name="Rackham1980">[[Rackham, Oliver]] (1980). ''Ancient woodland: its history, vegetation and uses''. Edward Arnold, London</ref> describes ''Ulmus'' as the most critical genus in the entire British flora, adding that 'species and varieties are a distinction in the human mind rather than a measured degree of genetic variation'. Eight species are endemic to North America and three to Europe, but the greatest diversity is in Asia with approximately two dozen species.<ref name="Fu" /> The oldest fossils of ''[[Ulmus]]'' are leaves dating [[Paleocene]], found across the Northern Hemisphere.<ref>{{Cite journal |last1=Zhang |first1=Qiu-Yue |last2=Huang |first2=Jian |last3=Jia |first3=Lin-Bo |last4=Su |first4=Tao |last5=Zhou |first5=Zhe-Kun |last6=Xing |first6=Yao-Wu |date=December 2018 |title=Miocene Ulmus fossil fruits from Southwest China and their evolutionary and biogeographic implications |url=https://linkinghub.elsevier.com/retrieve/pii/S0034666718301118 |journal=Review of Palaeobotany and Palynology |language=en |volume=259 |pages=198–206 |doi=10.1016/j.revpalbo.2018.10.007|bibcode=2018RPaPa.259..198Z |s2cid=135184883 }}</ref>

The classification adopted in the List of elm species is largely based on that established by Brummitt.<ref name="Brummitt">Brummitt, R. K. (1992). ''Vascular Plant Families & Genera''. Royal Botanic Garden, Kew, London, UK.</ref> A large number of synonyms have accumulated over the last three centuries; their currently accepted names can be found in the list of [[Elm synonyms and accepted names]].

Botanists who study elms and argue over elm identification and classification are called "pteleologists", from the Greek πτελέα (elm).<ref>Marren, Peter, ''Woodland Heritage'' (Newton Abbot, 1990).</ref>

As part of the order [[Urticales]], they are distantly related to [[cannabis]], [[mulberries]], [[fig]]s, [[hops]], and [[Urtica|nettle]]s.