'Regal', IBM, Portsmouth, UK
|Hybrid parentage||'Commelin' × '215' (U. pumila × 'Hoersholmiensis')|
Ulmus 'Regal' is an American hybrid elm cultivar developed by the University of Wisconsin–Madison and released in 1983. 'Regal' was derived from seeds arising from the crossing of the Dutch hybrid clones 'Commelin' and '215' (Ulmus pumila × 'Hoersholmiensis') sent in 1960 by Hans M. Heybroek of the De Dorschkamp Research Institute in the Netherlands.
'Regal' has a strong central leader bestowing an upright columnar form similar to 'Commelin', making it particularly suitable for street planting. The foliage is distinctively sparse, allowing dappled sunlight beneath the canopy . The leaves are narrowly elliptical, 5 cm to 10 cm in length, fern green when young, changing to a glossy, trichome-free, dusky spinach green. The perfect, wind-pollinated apetalous flowers emerge in early March.
Pests and diseases
'Regal' has a good resistance, rated 4 out of 5, to Dutch elm disease  and verticillium wilt, but is very susceptible to the Elm Leaf Beetle Xanthogaleruca luteola in the USA. The tree's foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the University of Missouri .
The tree performed particularly well in the Northern Arizona University trials  where, along with 'Frontier', it proved very tolerant of the hot and arid conditions in the eastern part of Arizona, exhibiting minimal leaf scorch. In Europe, 'Regal' was introduced by the now-defunct Conrad-Appel nursery in Darmstadt and grown under licence by several Dutch and German nurseries as one of the Resista series . It has enjoyed modest success in Germany as a street tree  , but remains uncommon in the UK, where it was introduced by the Conservation Foundation and marketed for a few years by Crowder's Nursery, near Lincoln. 'Regal' also featured in trials in New Zealand during the 1990s at the Hortresearch station, Palmerston North.
The UK TROBI champion is at Abbey Park, Leicester, measuring 14 m high, 26 cm d.b.h. in 2004. Several specimens are grown in the grounds of IBM's UK & European headquarters at North Harbour, Portsmouth.
- Chicago Botanic Garden, Glencoe, Illinois. 3 trees, no other details available.
- Holden Arboretum. Acc. no. 85-189
- Brighton & Hove City Council, UK, NCCPG Elm Collection . Some very big trees in Hangleton, Hove.
- Cambridge Botanic Garden , University of Cambridge, UK, no accession details available.
- Grange Farm Arboretum, Sutton St. James, Spalding, Lincolnshire, UK.
- Rombergpark , Dortmund, Germany. Details not known.
- Royal Horticultural Society Harlow Carr Arboretum , Harrogate, UK. Planted 1988.
- North America
- Johnson's Nursery , Menomonee Falls, Wisconsin
- Klyn Nurseries , Perry, Ohio
- Lake County Nursery , Perry, Ohio
- Sun Valley Garden Centre , Eden Prairie, Minnesota
- Eisele GmbH & Co KG Darmstadt, Germany.
- Golden Hill Plants , Marden, Kent, UK.
- Noordplant , Glimmen, Netherlands.
- Santamour, J., Frank, S. & Bentz, S. (1995). Updated checklist of elm (Ulmus) cultivars for use in North America. Journal of Arboriculture, 21:3 (May 1995), 121-131. International Society of Arboriculture, Champaign, Illinois, USA.
- Smalley, E. B. & Lester, D. T. (1983), HortScience 18: 960-961, 1983.
- 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 9789050112819
- Burdekin, D. A. & Rushforth, K. D. (Revised by Webber J. F. 1996) and Elms resistant to Dutch elm disease. Arboricultural Research Note 2/96. Arboricultural Advisory and Information Service, Alice Holt, Farnham, UK.
- http://www.extension.iastate.edu/Publications/SUL4.pdf Summary, inc. photographs, of elm cultivars resistant to Dutch elm disease available in the USA.
- http://fletcher.ces.state.nc.us/programs/nursery/metria/metria11/warren/elm.htm Warren, K., J. Frank Schmidt & Son Co. (2002). The Status of Elms in the Nursery Industry in 2000.