Dr Max Coleman of Royal Botanic Garden Edinburgh argued in his 2002 paper 'British Elms' that there was no clear distinction between species and subspecies.

[4][5] The smooth-leaved elm is a deciduous tree that can grow to 35 m. Its Latin synonym carpinifolia alludes to the superficial similarity of the leaves to those of hornbeam Carpinus sp., while the common names contrast the smooth upper surface and narrowness of the leaves with those of the wych elm, which are rough and broad.

Research currently (2009) in hand by Cemagref at Le Pepiniére forestiére de l'Etat, Guémené-Penfao, France, should confirm this.

However, all smooth-leaved elm varieties are believed to have been introduced into Britain from central and southern Europe during the Bronze Age,[8] and some, being beyond their natural climates and environments, may be growing slowly and thus producing smaller springwood vessels restrictive to the Ophiostoma fungus.

Moreover, several types of this subspecies also have very pendulous twigs when mature, a factor which could also make them unattractive to foraging Scolytus beetles, which are disinclined to invert themselves.

[16][17][18] Among "varieties with most resistance", Professor Oliver Rackham noted (1986) the 'Boxworth elm',[19] still thriving (2022)[20] in and around Boxworth, Cambridgeshire,[21] and from c.2010 propagated experimentally by the Conservation Foundation.

Results from Spain (2013), for example, confirm that a very small number of surviving field elms (about 0.5% of those tested) appear to have comparatively high levels of tolerance of the disease, and it is hoped that a controlled crossing of the best of these will produce resistant Ulmus minor hybrids for cultivation.

minor), Elwes noted (1913) that in Hertfordshire and along the western borders of Essex "the most graceful form of this tree may be seen in perfection".