Ulmus minor subsp. minor

Ulmus minor" subsp. "minor, the narrow-leaved elm (also known as smooth-leaved elm or East Anglian elm), was the name used by R. H. Richens (1983) for English field elms that were not English elm, Cornish elm, Lock elm or Guernsey elm. Many publications, however, continue to use plain "Ulmus minor" for Richens's subspecies, a name Richens reserved for the undifferentiated continental field elms. ("Ulmus minor" is native to southern Europe and Asia Minor including Iran.) 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. 
Description.
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. The apetalous perfect wind-pollinated flowers, and fruit (samaras) are very similar to those of the species.
Pests and diseases.
Although the smooth-leaved elm is generally susceptible to Dutch elm disease, it is genetically a highly variable tree and it is possible some specimens survive in the UK owing to an innately high level of resistance (see Cultivation). Research currently (2009) in hand by Cemagref at , 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, and some, being beyond their natural climates and environments, may be growing slowly and thus producing smaller springwood vessels restrictive to the "Ophiostoma" fungus. Good performance in the field may also be owing to resistance to bark beetle feeding or breeding. 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.
As the tree suckers readily, its genetic resources are not considered endangered.
The subspecies has a moderate to high susceptibility to the elm leaf beetle, "Xanthogaleruca luteola", and a moderate susceptibility to elm yellows.
Cultivation.
Many mature specimens still survive in England, notably in East Anglia. The Woodland Trust currently lists (2013) some 120 surviving "ancient" smooth-leaved elms in England and Wales, some of which are among the elms now being cloned, propagated and planted as part of The Conservation Foundation's 'Great British Elm Experiment' and 'Ulmus londinium' projects, a scheme to identify disease-resistant strains and return elms to city and countryside. Among "varieties with most resistance", Professor Oliver Rackham noted (1986) the 'Boxworth elm', still thriving (2022) in and around Boxworth, Cambridgeshire, and from c.2010 propagated experimentally by the Conservation Foundation. 
In a more academically-based project, most of the clones of the surviving European field elms that have been tested since the 1990s for innate resistance to Dutch elm disease by national research institutes in the EU, with a view to returning field elm to cultivation in Europe, would be classified by Richens’s system as "Ulmus minor" subsp. "minor". 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.
Narrow-leaved elm was occasionally planted as an ornamental urban tree.
Notable trees.
The largest recorded tree in the UK grew at Great Amwell in Hertfordshire, measuring 40 m in height and 228 cm diameter at breast height (d.b.h.) in 1911. Another famous specimen was the great elm that towered above its two siblings at the bottom of Long Melford Green, Long Melford, Suffolk, till the group succumbed to disease in 1978. The three "were survivors of a former clone of at least nine elms, one dating from 1757". The Long Melford elms were painted in 1940 by the watercolourist S. R. Badmin in his 'Long Melford Green on a Frosty Morning', now in the Victoria and Albert Museum.
The largest known surviving trees are at East Coker, Somerset (30 m high, 95 cm d.b.h.), Termitts Farm near Hatfield Peverel, Essex (25 m high, 145 d.b.h.), and Melchbourne, Bedfordshire, (147 cm d.b.h.).
Hybrids.
The tree's natural range in eastern England overlaps with that of wych elm ("Ulmus glabra"), the two species hybridizing to produce elms of the "Ulmus" × "hollandica" type. "U. minor" subsp. "minor" is believed to have hybridized also with Plot's elm to create "Ulmus" × "viminalis".