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The American elm is a deciduous tree which, under ideal conditions, can grow to heights of 21 to 35 meters (69 to 115 feet). [3] The trunk may have a diameter at breast height (dbh) of more than 1.2 m (4 ft), supporting a high, spreading umbrella-like canopy.
'Moline' is distinguished by its narrow but open form, with a single central trunk likened to a Lombardy Poplar when young, [4] the branches of the older trees being ultimately horizontal. [5] The leaves, of a dark rich shade of green, [ 6 ] could be exceptionally broad, measuring 15 cm across.
The tree can grow to greater than 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 American Elm cultivar Ulmus americana 'St. Croix' is a recent (2008) selection cloned from a large tree growing on a farm near Afton, Minnesota, [1] which has displayed a high resistance to Dutch elm disease (DED). [2] A U S patent, PP 20097, was granted in 2009.
The tree is highly resistant to Dutch elm disease. [1] No other specific information is available, but the species as a whole is highly susceptible to Elm Yellows; it is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola, [3] and highly preferred for feeding by the Japanese Beetle Popillia japonica [4] [5] in the United States.
As implied by its name, the tree has a fastigiate, columnar form, [4] of almost equal width from the base to a top which is rather flat in appearance. [2] " The leaves differ from those of the common form," wrote Rehder (1922), "in being rather broad, measuring up to 7.5 cm. in width, very sharply and deeply doubly serrate, scabrous above, pilose on the veins and veinlets beneath and very ...
The American elm cultivar Ulmus americana 'Lewis & Clark' (trade name Prairie Expedition) is a development from the North Dakota State University (NDSU) Research Foundation breeding programme, released in 2004 to commemorate the 200th anniversary of the eponymous expedition. [1]
The resistance of 'Jackson' to Dutch Elm Disease had not as of 1995 been confirmed by artificial inoculation. [1] The species as a whole is highly susceptible to Dutch Elm Disease and Elm Yellows; it is also moderately preferred for feeding and reproduction by the adult Elm Leaf Beetle Xanthogaleruca luteola, [3] and highly preferred for feeding by the Japanese Beetle Popillia japonica [4] [5 ...