Ulmus glaucescens

Ulmus glaucescens
Scientific classification
Kingdom:Plantae
Clade:Angiosperms
Clade:Eudicots
Clade:Rosids
Order:Rosales
Family:Ulmaceae
Genus:Ulmus
Subgenus:U. subg. Ulmus
Section:U. sect. Ulmus
Species: U. glaucescens
Binomial name
Ulmus glaucescens

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]

Description

Although typically no more than 10 m in height, it 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.

Pests and diseases

The tree is resistant to Dutch elm disease; it is also very resistant to the elm leaf beetle Xanthogaleruca luteola. [2]

Cultivation

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 Europe or Australasia. There are no known cultivars of this taxon, nor is it known to be in commerce.

Subspecies & varieties

Two varieties are recognized: var. glaucescens Rehder, and var. lasiocarpa L.K.Fu.

Accessions

North America

Nurseries

None known

References

  1. ↑ Fu, L., Xin, Y. & Whittemore, A. (2002). Ulmaceae, in Wu, Z. & Raven, P. (eds) Flora of China, Vol. 5 (Ulmaceae through Basellaceae). Science Press, Beijing, and Missouri Botanical Garden Press, St. Louis, USA.
  2. ↑ Miller, Fredric; Ware, George (2001-02-01). "Resistance of Temperate Chinese Elms (Ulmus spp.) to Feeding by the Adult Elm Leaf Beetle (Coleoptera: Chrysomelidae)". Journal of Economic Entomology. Oxford University Press (OUP). 94 (1): 162–166. doi:10.1603/0022-0493-94.1.162. ISSN 0022-0493.
  3. ↑ Ware, G. (1995). Little-known elms from China: landscape tree possibilities. Journal of Arboriculture, (Nov. 1995). International Society of Arboriculture, Champaign, Illinois, US. Archived 2007-11-30 at the Wayback Machine.
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