Ulmus × hollandica 'Pitteurs' or 'Pitteursii', one of a number of hybrid cultivars arising from the crossing of the Wych Elm Ulmus glabra with a variety of Field Elm Ulmus minor, was first identified by Morren as l'orme Pitteurs (1848). Elwes and Henry (1913) and Krüssmann (1976) listed it as an Ulmus × hollandica cultivar.Krüssmann, Johann Gerd, Handbuch der Laubgehölze (Vol. 3) (Paul Parey, Berlin and Hamburg, 1976); trans. Michael E. Epp, Manual of Cultivated Broad-Leaved Trees and Shrubs (Vol. 3) (Batsford, Timber Press, Beaverton, Oregon, 1984-6), p.410 It was named after the landowner Henri Bonaventure Trudon de Pitteurs of Saint-Trond, near Liège, Belgium, who discovered and first propagated the tree on his estate.

Description 'Pitteurs' was a tall tree, chiefly distinguished by its large, rounded, convex leaves, < 20 cm long by < 19 cm broad, a little attenuate at the apex and with prominent venation. Long shoots. Sheet described as U. montana With. f. hollandica Hort. = Pitteursii Ch. Morren; Short shoots. Sheet described as U. hollandica pitteursii / U. hollandica Mill. var. pitteursii Rehder; Sheet described as Ulmus montana With. f. hollandica Hort. = Pitteursii Ch. Morren, 1903; "Herbarium specimen BR0000027730775V". Botanic Garden, Meise. Sheet labelled Umus pitteursii, Liège botanical garden specimen (1904); Sheet described as U. Pitteursii gigantea, renamed U. hollandica Mill. var. pitteursii Rehder Kirchnerkiki.huh.harvard.edu/databases/botanist_search.php?id=2793 and Petzold,kiki.huh.harvard.edu/databases/botanist_search.php?id=2792 describing a tree by that name from the Royal State Tree Nursery at Sanssouci, noted (1864) that the slightly glossy dark green leaves were obtuse-toothed, and appeared reddish-brown when they unfolded. Aigret, however, reported (1905) that the specimen in the Jardin Botanique de Liège, planted in Morren's time, did not match Morren's description, having leaves of ordinary U. montana [used both for wych and for Ulmus × hollandica] dimensions, and being more elongated and acuminate than those described. This suggests that Morren's measurements for 'Pitteurs', like his measurements for 'Superba', may have been based on the largest of long-shoot leaves.

Cultivation Reputedly one of two varieties grown from seed obtained in 1845 by Henri de PitteursSchelev, A. (1854) Annuaire statistique et historique belge, page 325, Brussel - Leipzig of Sint-Truiden or Saint-Trond, near Liège, Belgium, the tree was planted on his estate and along roadsides in the region. (The second variety may have been the Ulmus hollandica belgica St.Trons in The Hague, listed separately from 'Belgica' and 'Pitteurs' by Christine Buisman in 1933.Christine Buisman, 'Verslag van de onderzoekingen over de iepenziekte, verricht in het phytopathologisch laboratorium Willie Commelin scholten te Baarn, gedurende 1932 (1)', Tijdschrift over Planteziekte, Vol 39 Iss 4, April  1933, p.85) Gillekens noted in 1891 that in the areas of Liège and Limbourg, 'Pitteurs' was preferred to 'Belgica'.Gillekens, Léopold Guillaume, Éléments d'arboriculture forestière (1891), p.40 Augustine Henry (1912) thought the tree, which produced shoots growing almost one metre a year, probably identical with those called orme Saint-Trond he saw at Looymans' nursery at Oudenbosch, which he considered perhaps identical when young to a variety of Ulmus montana occasionally sold as var. macrophylla. An elm said to be similar and also cultivated on the Pitteurs estate was 'Folia Rhomboidea'.

'Pitteurs' was distributed as Ulmus campestris Pittersii by the Baudriller nursery, Angers.Baudriller Établissement d'Horticulture, Catalogue général descriptif et raisonné des arbres fruitiers, forestiers & d'ornement cultivés dans l'établissement. Année. 1880, p.117 The Späth nursery of Berlin sold an elm which they said went by the name of 'Pitteurs' in some nurseries but which they themselves called U. hollandica.Späthbuch 1720-1920, p.263 They continued to distribute it till the late 1930s.Späth, L., Hauptkatalog der Baumschule 1937 (Berlin 1937), p.109 A specimen stood in Cantons Park, Baarn, in the interwar period. Sheet labelled Ulmus pitteursii Ch. Morren, Baarn, 1931; twig and flowers The Hesse nursery of Weener, Germany, marketed 'Pitteurs' in the 1930s as Ulmus latifolia, adding " = U. hollandica or U. pitteursi ", and in the 1950s as U. hollandica pitteursi.Hesse, Hermann A., Hauptkatalog 1956/57 (Weener, Ems, 1956); p.141-142

By 1900 there was a regular annual supply from the Netherlands (initially mainly from Oudenbosch, later from Opheusden) of several thousand 'Pitteurs' and 'Vegeta' to the Duchy of Schleswig and to Schleswig-Holstein, for coastal planting. After 1920 the numbers decreased as more elms began to be cultivated locally. With the spread, however, of the first Dutch elm disease epidemic, elm planting ceased in the area around 1930, and tens of thousands of unsellable 'Pitteurs' in nurseries had to be destroyed. They were often dug up for free by the unemployed, for use as firewood.

The Ulmus gras introduced to the USA c.1871, "a fine pyramidal-growing variety",Descriptive Catalogue of Ornamental Trees & Shrubs, no.2, Mount Hope Nurseries, New York, 1871; p.6Ellwanger & Barry, Descriptive Catalogue of Hardy Ornamental Trees ... at the Mount Hope Nurseries (Rochester, N.Y., 1875) distinguished in catalogues from 'Belgica', may have been Orme gras ('Pitteurs'). It was later renamed Ulmus montana grassei by some nurseries.W. T. Smith nursery, Geneva, New York, 1912W. T. Smith nursery, Geneva, New York, 1923 'Pitteurs' was present in the Arnold Arboretum, Massachusetts, in the interwar years.Ulmus hollandica var. Pitteursii, Arnold Arboretum, 1930 bioportal.naturalis.nl, specimen L.1587026

In 1998 an unsuccessful search of the de Pitteurs-Hiegaerts Estate (now in the public domain and known as the Speelhof park) was mounted in an attempt to rediscover the elm.Driesen, W. (2008), Stedelijke bibliotheek de Leidrad, Sint-Truiden It is assumed the cultivar fell victim to Dutch elm disease, as did thousands of other elms in the same district. However, 'Pitteurs' was known to have been marketed (as U. montana 'Pitteursi') in Poland in the 19th century by the Ulrich nursery,Ulrich, C. (1894), Katalog Drzew i Krezewow, C. Ulrich, Rok 1893–94, Warszawa Warsaw, and so may still survive in Eastern Europe. Several trees were thought to survive in England, in the Brighton area.Johnson, Owen (ed.) (2003). Champion Trees of Britain & Ireland. Whittet Press, . 'Pitteurs' is not known to have been introduced to North America or Australasia.

Putative specimens A pruned U. × hollandica with large, rounded, convex leaves, and obtuse teeth, exactly matching Morren's 1848 leaf-drawing of 'Pitteurs', stands in Portland Road, Hove (2016).

A second tree, also pruned, in Hove Recreation Ground,Hove Recreation Ground, west side; one tree north from central path.'Rare elms in the spotlight for Sussex Tree Festival', 11 June 2025 has leaves matching a Royal Botanic Garden Edinburgh 1903 'Pitteurs' herbarium specimen.data.rbge.org.uk, specimen E00824745

A putative specimen in the Extra Mural Cemetery in Brighton, was blown down in the Great Storm of 1987 (see gallery).

Accessions None known.

Hybrid cultivars 'Pitteurs' was crossed with other Ulmus × hollandica in the Dutch elm breeding programme before World War II, but none of the progeny were retained.Went, J. C. (1954). The Dutch elm disease - Summary of 15 years' hybridisation and selection work (1937–1952). European Journal of Plant Pathology, Vol 60, 2, March 1954.

Synonymy l'Orme gras ?l'Orme St. Trond Ulmus campestris latifolia, foliis rotundata: Morren, Journal d'agriculture pratique 4: 509, 511, 1851. Ulmus campestris var pitteursii: Wesmael in Bulletin de la Fédération des sociétés d'horticulture de Belgique 1862: 382, 1863. Ulmus scabra macrophylla Hort.: Dieck, (Zöschen, Germany), Haupt-catalog der Obst- und gehölzbaumschulen des ritterguts Zöschen bei Merseburg 1885 p. 82.

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