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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 viable pollen, through the activity of pollinators. One of the possible pollinators to assist in cross-pollination are honeybees.
Ulmus americana, generally known as the American elm or, less commonly, as the white elm or water elm, [a] is a species of elm native to eastern North America. The trees can live for several hundred years.
After pollination, seeds of spring-flowering elms ripen and fall at the start of summer (June); they remain viable for only a few days. They are planted in sandy potting soil at a depth of 1 cm, and germinate in three weeks. Slow-germinating American elm will remain dormant until the second season. [12]
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]
The perfect apetalous wind-pollinated flowers are vernal, appearing before the leaves unfold, born in long-pedicelled fascicles of 3 or 4. The fruit is a samara maturing in the spring as the leaves unfold; about 12 mm (½ inch) long, oval to oblong-obovate, deeply notched at apex, margin ciliate with smooth surfaces.
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 ...
The American Elm cultivar Ulmus americana 'Delaware' was originally selected (as tree number 218, a c.1940 seedling from North Dakota) ...
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).