Ulmus minor 'Plotii'

Ulmus minor
'Plotii', near Fineshade, 1911
Cultivar	'Plotii'
Origin	England

The Field Elm cultivar Ulmus minor 'Plotii', commonly known as Lock Elm or Lock's Elm (its vernacular names), Plot's Elm or Plot Elm, is found growing naturally only in England, where it is encountered mainly in the East Midlands, notably around the River Witham in Lincolnshire, in the Trent Valley around Newark on Trent^[1] and in the village of Laxton, Northamptonshire. It has been described as Britain's rarest native elm, and it is recorded by The Wildlife Trust as a nationally scarce species.^[2]

As with other members of the Field Elm group, the taxonomy of Plot Elm has been a matter of contention, several authorities^[3][4][5] recognizing it as a species in its own right. Indeed, it is as U. plotii that the specimens held by the Royal Botanic Gardens at Kew and Wakehurst Place are listed. 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,^[6][7] whereas Melville suggested the tree's distribution may be related to (river) valley systems.^[1] After Richens had challenged the species idea, the tree was the subject of a study at the Royal Botanic Garden Edinburgh by Dr Max Coleman (2000), which showed that trees that were a perfect fit with the 'type' material of Plot elm were of a single clone (genetically identical to each other).^[8] 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'.^[9]

Henry miscalled the tree Goodyer's Elm. The trees Goodyer discovered (U. minor 'Goodyeri') were near the coast at Pennington, Hampshire, some 200 miles away from their main centre of distribution and very dissimilar in structure.^[10][11][12]

Description

Before the advent of Dutch elm disease, this slender monopodial tree grew to a height of 30 m and was chiefly characterized by its cocked crown comprising a few short ascending branches; Richens^[13] likened its appearance to an ostrich feather.^[14] A single longish lower branch appears often to have been a feature of its profile.^[15] The obovate to elliptic acuminate leaves are small, rarely > 4 cm in length, with comparatively few marginal teeth, usually < 70; the upper surfaces dull, with a scattering of minute tubercles and hairs.^[16][17] The samarae rarely ripen, but when mature are narrowly obovate, < 13 mm in length, with a triangular open notch.^[10][11]

• 

  'Plotii', Banbury, 1911 (two contiguous trees)

• 

  Young Plot Elm, Laxton, Northamptonshire, 2015

• 

  Plot foliage, Madingley Road, Cambridge

• 

  Juvenile foliage, Laxton

• 

  Plot hedge, Caythorpe, Nottinghamshire

Pests and diseases

'Plotii' is very susceptible to Dutch elm disease.

Etymology

The tree was first classified by the Oxford botanist George Claridge Druce in 1907-11,^[18][19][20] who found examples at Banbury and Fineshade, Northamptonshire and published descriptions with photographs.^[21][22][23] Druce named the tree for Dr Robert Plot, a 17th-century English naturalist. The older vernacular name 'Lock Elm' is said to be an allusion to the difficulty in working its timber.^[24] However Druce wrote in 1913 that 'The wood is of very good quality, easy to work, and of a different texture from the Wych, Dutch, or English Elm, and has a general usefulness as a substitute for Ash or Wych Elm. The name Lock Elm can have no reference to any difficulty in working or dressing of the wood.'^[25] 'Lock' may be related to its use in boundaries, as 'loc' is Old English for enclosure.^[26] Richens, who had encountered the vernacular name 'Lock's Elm', called the tree U. minor. var. lockii.^[27] Bancroft referred to Plot's Elm as the 'East Anglian Elm', adding that it was often referred to as Wych Elm in the region;^[28] however, she was almost certainly alluding to the Smooth-leaved Elm.

Cultivation

Ulmus minor 'Plotii' locations in east Midlands, England, after Coleman (2000)^[8]

• 1. Derbyshire
• 2. Derby U.A.
• 3. Nottinghamshire
• 4. Nottingham U.A.
• 5. Lincolnshire
• 6. Leicestershire
• 7. Leicester U.A.
• 8. Rutland U.A.
• 9. Northamptonshire

As the two late-19th century specimens at Westonbirt Arboretum^[29] showed (mature by 1912 when Augustine Henry photographed one of them for his Trees of Great Britain & Ireland) and the tree at Eastington Park^[30][31] (mature by 1946), Plot-type elms had been noted as distinctive and were being included in collections before they were classified botanically by George Claridge Druce (1911). Melville confirmed by field studies in the 1930s that Druce's specimens^[32] were typical ('the type'),^[1] but believing plotii to be a species and so to some extent variable he also admitted to Kew 'Plot Elms' that varied from the type.^[33] Cultivation in the decades that followed, influenced by Melville or sourced from Kew, allowed similar latitude. Following Coleman's findings about the type (2000) and his paper on British elms (2002), atypical Plot's Elms or 'Plot-type' elms are classified as Ulmus aff. 'Plotii'. These are very close to Plot's Elm and have a number of characteristics of the type, but their crowns are too broad and regular to match "true Plot".^[8][9] It is now thought likely that the Westonbirt specimens were elms of the 'Plot-type' category.^[34]

An uncommon tree even before Dutch elm disease, 'Plotii' has also been affected by the destruction of hedgerows and by urban development within its limited range.^[2][35] No mature 'type' trees are known to survive. The last known stand of semi-mature Plot or Plot-type elms, the Madingley Road elms descended from those described by Elwes and Henry in 1913^[36] and by Richens in 1960,^[37] was destroyed by the City Council of Richens's own Cambridge in road-widening c.2007-2014.^[38] Unlike other forms of the Field Elm, 'Plotii' is not a prolific generator of suckers,^[39] but it is not considered critically endangered. Conservation measures were drafted to preserve known stands and to encourage propagation,^[2] though it is not clear if any of these were implemented.

"The Plot Elm is a beautiful tree," wrote Gerald Wilkinson, with "a silhouette no broader than Wheatley's." Wilkinson regarded as a "lost opportunity" the failure of East Midlands councils to cultivate this local elm in preference to exotic plantsmen's varieties. "Unhappily, the plumes of U. plotii are no longer a common feature of the landscape of the Trent above Newark and the Witham above Lincoln. Elms are now [1978] few in these areas that were once the home of Plot Elm. A wartime shortage of wood, altered drainage levels, land clearance for power stations, and machine farming have all combined into the familiar pattern of short-term efficiency and long-term degradation."^[40]

Outside botanical collections the 'type' tree was seldom planted as an ornamental,^[41] and it is no longer planted owing to its susceptibility to Dutch elm disease. It appears in National Elm Collection lists,^[42] but no specimen is known in the Brighton area (2015). The tree is not known in continental Europe, save three small (2014) specimens grown in a private garden at Seyne les Alpes, France.

Natural hybrids

Plot Elm hybridizes in the wild both with wych elm,^[1][43] to form U. × hollandica 'Elegantissima', and with U. minor to form Ulmus × viminalis. Melville noted that within the limits of the tree's distribution, hybrids are more common than Plot's Elm itself.^[1]

Hybrid cultivars

Elms of the Ulmus × viminalis group have been cultivated since the 19th century and have given rise to a hybrid cultivar of that name and to the cultivars 'Aurea', 'Marginata', 'Pulverulenta'.^[44] The 19th-century cultivar 'Myrtifolia' was considered by Melville to be a probable U. minor × U. minor 'Plotii' hybrid.^[45] The cultivar Wentworth Elm was identified by the Royal Botanic Garden Edinburgh as a hybrid of Huntingdon Elm and Plot Elm, though Melville dismissed the specimen growing at the Royal Botanic Gardens, Kew as Huntingdon Elm.^[46] The 20th-century dwarf elm cultivar 'Jacqueline Hillier' is thought to belong to the 'Elegantissima' group.^[47]

Notable trees

A mature avenue of the 'type' tree stood at Newton on Trent, Lincolnshire, in the early 20th century^[48] and a notable quantity grew by the river Tove at Towcester and was present until at least 1955.^[49]

The largest known quantity of Plot elm survives (2015) as a hedge of young trees near Caythorpe, Nottinghamshire.

The surviving Plot-type elm on Bruntsfield Links, Edinburgh (2015)^[50] (see Ulmus aff. 'Plotii') appears to have been planted as an example of Melville's 'species', though not of Druce's 'type'-tree. Its probable date of planting, the mid-20th century, coincides with Melville's paper drawing attention to this peculiar British elm.

The Plot Elm in art

George Lambert, 'View of Dunton Hall, Lincolnshire' (1739)

George Lambert's landscape 'View of Dunton Hall, Lincolnshire', painted in 1739 near Tydd St Mary within the native range of Plot Elm, shows a narrow monopodial elm-like tree with short branches and cocked crown, that may be a rare representation of Plot Elm in art. Tydd St Mary is not far from the River Welland, where Melville had noted the presence of Plot Elm.^[1]

Accessions

North America

• Bartlett tree nurseries. Acc. nos. 7771, 00–108, as U. plotii, provenances not disclosed.

Europe

• Brighton & Hove City Council, UK. NCCPG Elm Collection . No details available.
• Grange Farm Arboretum, Sutton St James, Spalding, Lincolnshire, UK. As U. minor 'Plotii'. Acc. no. 1081.
• Wakehurst Place Garden, Wakehurst Place, UK, as U. plotii. Acc. no. 1912-59402, donated by Augustine Henry, acc. nos. 1975–6181, 1975–6195, 1977–6692, all collected by Melville.
• Royal Botanic Gardens Kew, UK, as U. plotii, acc. no. 1969-16753, (planted 1958), donated by Melville.

References

External links

• 'The Plot Elm', resistantelms.co.uk
• 'Plot Elms' (Ulmus minor 'Plotii'), www.plot-elms.co.uk
• http://www.ipgri.cgiar.org/Networks/euforgen/Networks/Scattered_Broadleaves/NHStrategies/UlmusSppConsStrategy.htm.
• Ulmus minor var. plotii Action Plan, The Wildlife Trust
• Ulmus minor var. plotii, The Flora of Derbyshire, Derby City Council