Ulmus minor 'Christine Buisman' | |
---|---|
Species | Ulmus minor |
Cultivar | 'Christine Buisman' |
Origin | Netherlands |
The Field Elm cultivar Ulmus minor 'Christine Buisman' was the first cultivar released by the Dutch elm breeding programme, initiated in response to the less virulent form of Dutch elm disease (DED), Ophiostoma ulmi , which afflicted Europe's elms after the First World War. [1] 'Christine Buisman' was selected from a batch of 390 seedlings grown from seed collected in the Parque de la Quinta de la Fuente del Berro, Madrid, by Mrs Van Eeghen, a friend of elm researcher Johanna Westerdijk, in 1929 and named for the elm disease researcher Christine Buisman. [2] Originally identified as Ulmus foliacea (syn. U. minor), it was later treated as Ulmus × hollandica by Melville. [3] However, more recent research in Belgium using DNA markers has reaffirmed 'Christine Buisman' as a clone of U. minor. [4]
Originally identified as clone No. '24', it showed no symptoms of DED after several artificial inoculations. In later years, minor symptoms were detected on both the motherplant and grafted descendants, but these were considered too insignificant to delay its release to commerce as Ulmus 'Christine Buisman' in 1937.
The tree was deemed to have 'no outstanding ornamental characteristics', being 'broadly pyramidal, but 'irregular' in shape, notably the habit of one or two of the main branches initially growing out almost horizontally for about 1 m before curving upwards to the vertical, while outer branches can be long and pendulous. [2] Other authorities have been more generous, noting its straight trunk and relatively short and slender branches forming a small crown. The twigs are dark brown, strigose pubescent at first, becoming smooth. The alternate buds are ovoid, covered with a grey pubescence. The leaves are 7.0 cm long by 4.5 cm wide, very oblique at the base, with doubly serrate margins, smooth and dark green above, lighter below, and with prominent parallel veins covered with coarse white hair. The petiole is 10 millimetres (0.39 in) long. [5] [6] [7]
'Christine Buisman' was found to be highly resistant to the first strain of DED, O. ulmi, [8] but prone to some strains of Coral Spot fungus Nectria cinnabarina as it lacked resistance mechanisms. [9] In the US, the clone also proved highly resistant to elm yellows, [5] but very susceptible to Japanese beetles. [10]
The tree had not been thoroughly evaluated in the field before its release. However, such was the clamour for a resistant tree in the Netherlands, nurseries there raised and released large numbers, selling almost 10,000 per annum by the late 1930s. Once its shortcomings, which included poor resistance to sea winds, became apparent, commercial production soon ceased, [11] although by this time it had already been exported to Italy and the United States [9] where it was planted as a street tree. The tree can still be found in the Netherlands, notably in The Hague, Amsterdam, Wassenaar, [12] and Heiloo; in the UK it is largely restricted to Brighton. In North America, the tree has proved notably tolerant of heat, drought, and cold. In 1972, 1,000 trees were planted in Kansas City. [13] USDA Hardiness Zone 4 (−20 to −10 °F (−29 to −23 °C)). [10]
'Christine Buisman' was extensively trialled during the 1950s in the northern central states of the US by the USDA's Agricultural Research Service. The tree performed very well, and such losses that were sustained were attributable to climatic extremes, not disease. [5]
A large specimen planted in 1957 by Bernice Cronkhite in memory of Christine Buisman survives (2010) outside the Cronkhite Graduate Center, Harvard University, US. [14] A particularly impressive plantation exists in the US at Buffalo, along McKinley, Chapin, Bidwell, and Lincoln Parkways, [15] as well as Richmond Avenue and in Forest Lawn Cemetery. In the UK, the TROBI Champion is found on Palmeira Avenue, Hove, 12 metres (39 ft) high by 38 centimetres (15 in) d.b.h. in 2009. [16]
The tree is named for Christine Buisman, the first full-time elm researcher (1927-1936) in the Netherlands, who provided the final proof that Graphium ulmiSchwarz (now: Ophiostoma ulmi(Buisman) Melin & Nannf.) was the causal agent of Dutch elm disease. Buisman died in 1936, aged 36.[ citation needed ]
Ulmus × hollandica 'Vegeta', sometimes known as the Huntingdon Elm, is an old English hybrid cultivar raised at Brampton, near Huntingdon, by nurserymen Wood & Ingram in 1746, allegedly from seed collected at nearby Hinchingbrooke Park. In Augustine Henry's day, in the later 19th century, the elms in Hinchingbrooke Park were U. nitens. Richens, noting that wych elm is rare in Huntingdonshire, normally flowering four to six weeks later than field elm, pointed out that unusually favourable circumstances would have had to coincide to produce such seed: "It is possible that, some time in the eighteenth century, the threefold requirements of synchronous flowering of the two species, a south-west wind", "and a mild spring permitting the ripening of the samaras, were met."
Ulmus × hollandica 'Commelin' is a Dutch hybrid cultivar released for sale in 1960. The tree was raised at Baarn as clone 274 by the Foundation Willie Commelin Scholten Phytopathological Laboratory in 1940, from a crossing of Ulmus × hollandica 'Vegeta' and clone 1, an Ulmus minor selected from a 1929 elm seedlings lot obtained from the Barbier nursery, Orléans.
The Dutch hybrid cultivar Ulmus 'Dodoens' was derived from a selfed seedling of a crossing of the Exeter Elm Ulmus 'Exoniensis' with the Himalayan Elm Ulmus wallichiana at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. The tree was one of several cultivars prepared for release in 1970, but delayed by the outbreak of the second, far more aggressive strain of Dutch elm disease.
The Dutch hybrid elm cultivar Ulmus × hollandica 'Groeneveld' was cloned in 1949 at the De Dorschkamp Institute, Wageningen, and released in 1963 in response to the earlier, less virulent form of Dutch elm disease that afflicted Europe shortly after the First World War. The cultivar was derived from a crossing of Dutch clones '49', and '1', a Field Elm Ulmus minor found in central France and marketed by the Barbier nursery in Orléans.
Ulmus 'Homestead' is an American hybrid elm cultivar raised by Alden Townsend of the United States National Arboretum at the Nursery Crops Laboratory in Delaware, Ohio. The cultivar arose from a 1970 crossing of the Siberian Elm Ulmus pumila with the hybrid N 215, the latter grown from seed sent in 1960 to the University of Wisconsin-Madison elm breeding team by Hans Heybroek of the De Dorschkamp Research Institute in the Netherlands. Tested in the US National Elm Trial coordinated by Colorado State University, 'Homestead' averaged a survival rate of 85% after 10 years. 'Homestead' was released to commerce without patent restrictions in 1984.
Ulmus 'Lobel' is a Dutch hybrid cultivar raised at the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, from a crossing of clone '202' with '336'. 'Lobel' was cloned in 1962 and released for sale in 1973.
Ulmus × hollandicaMill. , often known simply as Dutch elm, is a natural hybrid between Wych elm and field elm Ulmus minor which commonly occurs across Europe wherever the ranges of the parent species overlap. In England, according to the field-studies of R. H. Richens, "The largest area [of hybridization] is a band extending across Essex from the Hertfordshire border to southern Suffolk. The next largest is in northern Bedfordshire and adjoining parts of Northamptonshire. Comparable zones occur in Picardy and Cotentin in northern France". Crosses between U. × hollandica and either of the parent species are also classified as U. × hollandica. Ulmus × hollandica hybrids, natural and artificial, have been widely planted elsewhere.
Ulmus 'Plantyn' was one of three Dutch hybrid elms released by the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen, in 1973. Derived from a crossing of the Dutch hybrids '202' and '302', it was to prove of great significance in later developments. A selfed seedling was to become the first Dutch clone to prove effectively immune to disease, released in 1989 as 'Columella'. 'Plantyn' was also destined to be the female parent of Lutèce released in 2002. In Italy, 'Plantyn' was used again as female parent in hybridizations with the Siberian Elm Ulmus pumila by the Istituto per la Protezione delle Piante (IPP), to create three new cultivars better adapted to the Mediterranean climate.
The hybrid elm cultivar Ulmus × hollandica 'Belgica', one of a number of hybrids arising from the crossing of Wych Elm with a variety of Field Elm, was reputedly raised in the nurseries of the Abbey of the Dunes, Veurne, in 1694. Popular throughout Belgium and the Netherlands in the 19th century both as an ornamental and as a shelter-belt tree, it was the 'Hollandse iep' in these countries, as distinct from the tree known as 'Dutch Elm' in Great Britain and Ireland since the 17th century: Ulmus × hollandica 'Major'. In Francophone Belgium it was known as orme gras de Malines.
The hybrid elm cultivar Ulmus × hollandica 'Dampieri', one of a number of cultivars arising from the crossing of the Wych Elm U. glabra with a variety of Field Elm U. minor, is believed to have originated in continental Europe. It was marketed in Wetteren, Belgium, in 1851 as 'Orme de Dampier', then in the Low Countries in 1853, and later identified as Ulmus campestris var. nuda subvar. fastigiata DampieriHort., Vilv. by Wesmael (1862).
Ulmus 'Columella' is a Dutch elm cultivar raised by the Dorschkamp Research Institute for Forestry & Landscape Planning, Wageningen. Originally thought to have been derived from a selfed or openly pollinated seedling of the hybrid clone 'Plantyn', DNA analysis later determined it arose from a cross of 'Plantyn' and Ulmus minor. Sown in 1967, it was released for sale in 1989 after proving extremely resistant to Dutch elm disease following injection with unnaturally high doses of the pathogen, Ophiostoma novo-ulmi. However, propagated by grafting onto wych elm rootstocks, graft failure owing to incompatibility has become a common occurrence in the Netherlands.
The Field Elm cultivar Ulmus minor 'Hoersholmiensis', Hoersholm elm, originated from seed sown at the Hørsholm Planteskole, Denmark, c. 1885, where it was propagated by the nursery proprietor Lars Nielsen. The Späth nursery of Berlin, however, which marketed 'Hoersholmiensis' in the interwar period, considered it a hybrid rather than a form of field elm, a view shared by Christine Buisman, who in 1931 labelled a herbarium specimen from a Späth-sourced tree in The Hague as a form of Ulmus × hollandica.
Ulmus 'Exoniensis', the Exeter elm, was discovered near Exeter, England, in 1826, and propagated by the Ford & Please nursery in that city. Traditionally believed to be a cultivar of the Wych Elm U. glabra, its fastigiate shape when young, upward-curving tracery, small samarae and leaves, late leaf-flush and late leaf-fall, taken with its south-west England provenance, suggest a link with the Cornish Elm, which shares these characteristics.
The elm cultivar Ulmus minor 'Bea Schwarz' was cloned at Wageningen in the Netherlands, by the elm disease committee, from a selection of Ulmus minor found in France in 1939. However, specimens of the tree grown in the UK and the United States are falsely treated as Ulmus × hollandica.
The elm cultivar Ulmus 'Hillieri' arose from a chance seedling at Hillier's Pitt Corner nursery near Winchester, England, in 1918, and was marketed from 1928 as Ulmus hillieri, a name accepted by Christine Buisman in her 1931 labelling of a specimen in France. Since at least 1944 the tree has been determined a form of Ulmus × hollandica, its designation at Kew Gardens, in Green, and in later Hillier catalogues. In 1940, 'Hillieri' was noted as being a hybrid of uncertain origin. Krüssmann notes that for a time the tree was listed by Hilliers as U. × hillieri.
The hybrid elm cultivar Ulmus 'Den Haag' is a Dutch development derived from a chance crossing of the Siberian Elm cultivar Ulmus pumila 'Pinnato-ramosa' and the Belgian Elm Ulmus × hollandica 'Belgica'. S. G. A. Doorenbos (1891-1980), Director of Public Parks in The Hague, finding that seeds he had sown in 1936 from the Zuiderpark 'Pinnato-ramosa' had hybridized with the local 'Belgica', selected six for trials. The best was cloned and grafted on 'Belgica' rootstock as 'Den Haag'; it was planted first in that city, then released to nurseries elsewhere in the Netherlands. The other five were also planted in The Hague.
The Field Elm cultivar Ulmus minor 'Schuurhoek' was originally an old, nameless clone cultivated c.1880 in the vicinity of Goes, Netherlands, which was taken back into cultivation as 'Schuurhoek' by the van't Westeinde nursery at 's-Heer Abtskerke, Zeeland, in the 1950s. It was identified as U. carpinifolia by Fontaine (1968), though treated as a cultivar of U. × hollandica by some authorities.
Ulmus × hollandica 'Klemmer', or Flanders Elm, is probably one of a number of hybrids arising from the crossing of Wych Elm with a variety of Field Elm, making it a variety of Ulmus × hollandica. Originating in the Bruges area, it was described by Gillekens in 1891 as l'orme champêtre des Flandres in a paper which noted its local name, klemmer, and its rapid growth in an 1878–91 trial. Kew, Henry (1913), and Krüssmann (1976) listed it as an Ulmus × hollandica cultivar, though Henry noted its "similarity in some respects" to field elm Ulmus minor, while Green went as far as to regard it as "possibly U. carpinifolia" (:minor).
The elm cultivar Ulmus 'Lombartsii' is considered "possibly Ulmus × hollandica or Ulmus carpinifolia " by Green (1964). The tree was raised by Lombarts Nurseries at Zundert, Netherlands, circa 1910.
Christine Johanna Buisman was a Dutch phytopathologist who dedicated her short career to the research of Dutch elm disease and the selection of resistant elm seedlings. In 1927, Buisman provided the final proof that Graphium ulmi was the causal agent of the disease, concluding the controversy which had raged among Dutch and German scientists since 1922.
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