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 20002600 m.[1]

Ulmus glaucescens
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
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

Description

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 MarchApril; 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
Europe

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. PMID 11233108.CS1 maint: ref=harv (link)
  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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