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. 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. The patent issued in 1975 has expired, and there are now no propagation restrictions.
Description
The tree usually forks at 1.5–2 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. 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.