| 词条 | Ulmus glaucescens |
| 释义 |
| image = | parent = Ulmus sect. Ulmus | display_parents = 2 | genus = Ulmus | species = glaucescens | authority = Franch. }}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] DescriptionAlthough 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. Pests and diseasesThe tree is resistant to Dutch elm disease; it is also very resistant to the elm leaf beetle Xanthogaleruca luteola. [2] CultivationThe 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 & varietiesTwo varieties are recognized: var. glaucescens Rehder, and var. lasiocarpa L.K.Fu. Accessions
References1. ^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. {{Elm species, varieties, hybrids, hybrid cultivars and species cultivars |state=collapsed}}{{Taxonbar|from=Q7879490}}2. ^{{cite journal | last=Miller | first=Fredric | last2=Ware | first2=George | title=Resistance of Temperate Chinese Elms (Ulmus spp.) to Feeding by the Adult Elm Leaf Beetle (Coleoptera: Chrysomelidae) | journal=Journal of Economic Entomology | publisher=Oxford University Press (OUP) | volume=94 | issue=1 | date=2001-02-01 | issn=0022-0493 | doi=10.1603/0022-0493-94.1.162 | pages=162–166 | ref=harv}} 3. ^Ware, G. (1995). Little-known elms from China: landscape tree possibilities. Journal of Arboriculture, (Nov. 1995). International Society of Arboriculture, Champaign, Illinois, US. {{Webarchive|url=https://web.archive.org/web/20071130221822/http://www.ces.ncsu.edu/fletcher/programs/nursery/metria/metria8/m87.pdf |date=2007-11-30 }} 6 : Ulmus|Trees of China|Flora of China|Trees of Asia|Ulmus articles missing images|Elm species and varieties |
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