Ulmus 'Sapporo Autumn Gold'
|Ulmus 'Sapporo Autumn Gold' subsp. var.|
'Sapporo Autumn Gold' is one of the most successful hybrid elm cultivars ever marketed, widely planted across North America and western Europe, although it has now been largely supplanted by more recent introductions . Arising from a chance crossing in 1958 of the Siberian Elm Ulmus pumila and the Japanese Elm Ulmus davidiana var. japonica in the Botanical Garden of Hokkaido University, Sapporo, it was cultivated at the University of Wisconsin–Madison by the late Prof. Eugene Smalley and patented in 1975  .
The tree forms a densely foliated vase-shaped crown, although immature plants produce vigorous side shoots that require assiduous pruning to develop the desired shape. The leaves are narrowly-elliptical, < 8.5 cm long by < 4.0 cm wide and, as the name implies, turn pale yellow in autumn. The perfect, apetalous wind-pollinated flowers appear in March, followed by the seeds in April; flowering usually begins when the tree is aged six years.
In favourable conditions, notably a moist, well-drained soil, the tree can grow at a rate of almost one metre per annum, but trials by the Northern Arizona University  found that it is not very tolerant of a hot, arid environment although its leaves sustain comparatively little scorch damage. Moreover, in trials in southern England conducted by Butterfly Conservation the tree was found to be intolerant of ponding over winter.
Pests and diseases
'Sapporo Autumn Gold' possesses a very high resistance to Dutch elm disease   and a tolerance of Verticillium wilt . The tree's foliage was adjudged "resistant" to Black Spot by the Plant Diagnostic Clinic of the University of Missouri , however it can be severely damaged the Elm Leaf Beetle Xanthogaleruca luteola in the USA 
- ↑ 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. (1973). HortScience 8: 514-515, 1973.
- ↑ Smalley, E. B. & Guries, R. P. (1993). Breeding Elms for Resistance to Dutch Elm Disease. Annual Review of Phytopathology Vol. 31 : 325-354. Palo Alto, California.
- ↑ Pinon, J., Lohou, C. & Cadic, A. (1998). Hybrid Elms (Ulmus Spp.): Adaptability in Paris and behaviour towards Dutch elm disease (Ophiostoma novo-ulmi). Acta Horticulturae 496, 107-114, 1998.
- ↑ Pinon, J. (2007). Les ormes résistants à la graphiose. Forêt-entreprise, No. 175 - Juillet 2007, p 37-41, France.
- ↑ 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.