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''Ulmus'' '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.〔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. () 〕 Arising from a chance crossing in 1958 of the Siberian Elm ''Ulmus pumila'' (female parent) 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.〔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.〕 The patent issued in 1975 has expired, and there are now no propagation restrictions. ==Description== The tree usually forks at between 1.5 m and 2 m from the ground to produce a broad, rounded, densely foliated crown, although immature plants produce vigorous side shoots requiring assiduous pruning to maintain shape. The bark is pale grey, and longitudinally fissured to form a random lattice pattern. The leaves are narrowly elliptical, < 9 cm long by < 4.5 cm wide, with 8 mm petioles. As the name implies, the leaves turn pale yellow in autumn.〔Photograph of autumn colouring of 'Sapporo' elm, ().〕 The perfect, apetalous wind-pollinated flowers appear in early March, followed by the seeds in April; flowering usually begins when the tree is aged six years. Image: Sapporo A G bark, Christchurch.jpg|Bark of 30-year-old tree. Image: Sapporo AG leaf.jpg|Foliage. Image: Sapporo A G, Christchurch.jpg|Coastal tree, Mudeford, UK. Image: Sapporo Autumn Gold unpruned 1.jpg|Tree left unpruned. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ulmus 'Sapporo Autumn Gold'」の詳細全文を読む スポンサード リンク
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