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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.
For the plant, the pollinizer, this can be an important mechanism for sexual reproduction, as the pollinator distributes its pollen. Few flowering plants self-pollinate ; some can provide their own pollen (self fertile), but require a pollinator to move the pollen; others are dependent on cross pollination from a genetically different source of ...
Testing in laboratory conditions by the United States Department of Agriculture from 1992 to 1993 revealed that 'Princeton' had some resistance to Dutch elm disease (DED), [6] [7] [8] although the original Princeton elm, which grew in Princeton Cemetery and was estimated to be over 150 years old, was felled in April 2005 after suffering 60 percent dieback, attributed by some accounts to Dutch ...
Serious infestations can cause plant death. Rose scale (order Hemiptera: family Coccoidea) Aulacaspis rosae – Mainly found on the stems and branches of the plant, lack of control will allow the pest to spread to flower stalks and petioles. At this point the plant would be stunted, spindly and with a white, flaky crust of scales on the bark.
It was steadily weakened by viruses in Europe and had all but disappeared by the 1940s. However, the disease had a much greater and longer-lasting impact in North America, owing to the greater susceptibility of the American elm, Ulmus americana, which masked the emergence of the second, far more virulent strain of the disease Ophiostoma novo-ulmi.
The American Elm cultivar Ulmus americana 'Jefferson' was cloned from a tree growing near a path in front of the Freer Gallery of Art, close to the Smithsonian Institution Building ("The Castle") on the National Mall in Washington, D.C. [1] The United States National Park Service, which had planted the tree during the 1930s, cloned it in 1993 after screening tests showed that it possessed an ...
Weeping elm by Plymouth Congregational Church, Plainfield, Illinois (1941) Morton Arboretum's Ulmus americana f. pendula (2009). The U. americana pendula planted at the Dominion Arboretum, Ottawa, in 1889 may have been Späth's mis-named Ulmus fulva (Mchx) pendula, later corrected in arboretum lists, since Späth supplied many of the 1880s' and 1890s' elms there. [14]
Ulmus americana var. floridana, the Florida elm, first described as Ulmus floridana by Alvan Wentworth Chapman in the 1860s, is smaller than the type, and occurs naturally in north and central Florida south to Lake Okeechobee. [1]