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The American Elm cultivar ''Ulmus americana'' 'Princeton' was originally selected in 1922 by New Jersey nurseryman William Flemer for its aesthetic merit. By coincidence, 'Princeton' was later found to have a moderate resistance to Dutch elm disease in the USA. ==Description== The tree can grow to > 30 m in height, and is distinguished by its dense, symmetrical, upright form and dark green foliage, ultimately forming a broad umbrella crown. Crotch angles can be acute, with considerable bark inclusion which can later lead to branch breakages. The leaves are < 16 cm long by 8 cm broad. 'Princeton' grows quickly, young trees increasing in height by over 1.6 m per annum (d.b.h. by 2.8 cm p.a.) in an assessment at U C Davis as part of the National Elm Trial.〔McPherson, G. ''et al''. (2008). National elm trial: Initial report from Northern California. ''Western Arborist'', Fall 2009, pp 32-36.〕 The tree commences flowering aged nine years. Image: Princeton leaf.JPG|'Princeton' leaf Image:Princeton Elm foliage damage.jpg|Typical foliage damage sustained in England Image:Princeton, bark inclusion.jpg|Crotch with bark inclusion 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ulmus americana 'Princeton'」の詳細全文を読む スポンサード リンク
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