Ulmus 'Clusius'

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Ulmus hybrid cultivar
RN Ulmus Clusius.JPG
Ulmus 'Clusius', Netherlands.
Hybrid parentage ('Exoniensis' × U. wallichiana) × 'Bea Schwarz' selfed
Cultivar 'Clusius'
Origin Wageningen, The Netherlands

Ulmus 'Clusius' is a Dutch hybrid elm cultivar raised at Wageningen and released to commerce in 1983. 'Clusius' was derived from a crossing of the same Dutch clones that produced the fastigiate 'Lobel' released in 1973: '202' ('Exoniensis' × U. wallichiana) and '336' ('Bea Schwarz' selfed).

Description[edit]

Clusiusleaves2008.jpg

The tree has a broader crown than its siblings', whilst the generally obovate leaves, < 11 cm long by 7 cm wide, are less acuminate at the apex.[1][2] Like 'Lobel', the tree flushes markedly later than most other elms, and is rarely in full leaf before mid-May.

Pests and diseases[edit]

Whilst the resistance of 'Clusius' to Dutch elm disease proved marginally greater than that of its Dutch predecessors, rated 4 out of 5,[3] it has been eclipsed by later developments such as Lutèce. Consequently, sales in the Netherlands declined from over 8,000 in 1979 to 600 in 2004[4] [1].

Cultivation[edit]

While 'Clusius' remains for sale in Europe, its planting where the disease remains prevalent cannot be recommended.[5] 'Clusius' featured in New Zealand government trials during the 1990s at the Hortresearch station, Palmerston North, but is not known to have been introduced to North America.

Etymology[edit]

The cultivar is named for Carolus Clusius, a Dutch naturalist of the Renaissance.

Accessions[edit]

Europe

Nurseries[edit]

References[edit]

  1. ^ Heybroek, Hans M. (1983). Burdekin, D.A., ed. "Resistant elms for Europe" (PDF). Forestry Commission Bulletin (Research on Dutch elm disease in Europe). London: HMSO (60): 108–113. 
  2. ^ Heybroek, H. M. (1993). The Dutch Elm Breeding Program. In Sticklen & Sherald (Eds.) (1993). Dutch Elm Disease Research, Chapter 3. Springer Verlag, New York, USA
  3. ^ Heybroek, H. M., Goudzwaard, L, Kaljee, H. (2009). Iep of olm, karakterboom van de Lage Landen (:Elm, a tree with character of the Low Countries). KNNV, Uitgeverij. ISBN 978-90-5011-281-9
  4. ^ Hiemstra, J.A. et al. (2007). Belang en toekomst van de iep in Nederland. Praktijkonderzoek Plant & Omgeving, Wageningen UR, Netherlands.
  5. ^ Burdekin, D. A. & Rushforth, K. D. (Revised by Webber J. F. 1996). Elms resistant to Dutch elm disease. Arboricultural Research Note 2/96. Arboricultural Advisory and Information Service, Alice Holt, Farnham, UK.