Ulmus glaucescens Franch., the Gansu elm, is a small deciduous tree from the northern provinces of China, where it is found along river valleys and on mountain slopes at elevations of 2000–2600 m.[1]
Although typically no more than 10 m in height, U. glaucescens can occasionally reach 18 m. Slow growing, the tree is possessed of a stiff branching pattern resembling that of a young American elm. The bark is longitudinally fissured and occasionally exhibits a peeling, mottled pattern. However, the tree is most easily distinguished by its small leaves; ranging from ovate to lanceolate, their size rarely exceeds 5 cm in length by 2.5 cm breadth, and are borne on twigs devoid of corky wings or layers. The perfect wind-pollinated apetalous flowers are produced on second-year shoots in March–April; the samarae are elliptic, < 25 mm long, and can remain on the tree until the end of May.
The tree is resistant to Dutch elm disease; it is also very resistant to the elm leaf beetle Xanthogaleruca luteola. [2]
The tree is notable for its resistance to extreme drought which, combined with its high resistance to the elm leaf beetle in the United States, has made it a contender for establishment on the Great Plains. Like most other Asiatic species, it is intolerant of wet ground. The tree is very rare in cultivation, but was one of a number of Chinese elms assessed for their horticultural potential at the Morton Arboretum, Illinois, during the last quarter of the 20th century.[3] It is not known to have been introduced to Australasia. There are no known cultivars of this taxon, nor is it known to be in commerce.
Two varieties are recognized: var. glaucescens Rehder, and var. lasiocarpa L.K.Fu.
Ulmus glaucescens Franch., the Gansu elm, is a small deciduous tree from the northern provinces of China, where it is found along river valleys and on mountain slopes at elevations of 2000–2600 m.
