Search results
Results from the WOW.Com Content Network
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.
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.
The starting-points for List of elm cultivars, hybrids and hybrid cultivars were fourfold: (1) Green's 'Registration of Cultivar Names in Ulmus ' (1964), [1] based on the contemporary nomenclature of elm species and wild hybrids; (2) Krüssmann's confirmation or correction of cultivar-names in his monumental Handbuch der Laubgehölze (1976); [2] (3) Heybroek's table of Netherlands research ...
The American Elm cultivar Ulmus americana 'Princeton' was originally selected in 1922 by New Jersey nurseryman William Flemer of Princeton Nurseries for its aesthetic merit. 'Princeton' was later found to have a moderate resistance to Dutch elm disease (DED).
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.
Research to select resistant cultivars and varieties began in the Netherlands in 1928, followed by the United States in 1937 (see Ulmus americana cultivars). Initial efforts in the Netherlands involved crossing varieties of U. minor and U. glabra, but later included the Himalayan or Kashmir elm U. wallichiana as a source of antifungal genes.
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]