|Russian Elm - Ulmus laevis|
Family Ulmaceae - Zelkova, Hackberry, Elm
Russian elm is adapted to waterlogged soil and is often found near watercourses.
Russian elm is also commonly called Fluttering Elm, Spreading Elm, and European White Elm. It is a large tree native to Europe, from France northeast to southern Finland, and southeast to Bulgaria and the Crimea; there is also a population in the Caucasus. Essentially a riparian species, it is commonly encountered along the Volga and Danube rivers. It is the only elm tolerant of waterlogged ground, its massive shallow root system forming distinctive high buttresses around the trunk.
|Like other European elms, it has little resistance to Dutch elm disease, but is eschewed by the vector bark beetles and only rarely becomes infected. Research published in the Canadian Journal of Forest Research has indicated that it is the presence of certain organic compounds, such as triterpenes and sterols, that serves to make the tree bark unattractive to the beetle species that spread the disease. Its decline in Europe is chiefly owing to woodland clearance in river valleys.|
The Morton Arboretum, at Lisle, Illinois, is home to the largest Elm collection in North America. Under study, the collection includes almost all of the 22 Elm species native to China, a dozen of which show resistance to Dutch elm disease and elm yellows. The Arboretum in past years has bred and marketed five new elm varieties resistant to Dutch elm disease.
The 12 species being studied are: the Bergmann (Ulmus bergmanniana), Taihang Mountain (U. taihangshanensis), Tibetan (U. microcarpa), Anhui (U. gaussenii), Hebei (U. lamellosa), Harbin (U. harbinensis), corkbark (U. propinqua var. suberosa), plum-leaved (U. prunifolia), Chenmou (Ulmus chenmoui), Gansu (Ulmus glaucescens var. lasiocarpa), chestnut-leaved (U. castaneifolia) and Father David (U. davidiana var. mandshurica) elms.
These 12 Chinese trees are virtually unknown in the U.S., but are under close study at the arboretum. Dendrologist Emeritus and former research director Dr. George Ware, and Arboretum Assistant Director of Collections Kunso Kim are responsible for their observation and data collection. Their efforts may help ameliorate the effects of numerous maladies affecting trees around the world, such as Emerald Ash Borer, Oak wilt, Asian Longhorned Beetle, Pine Sawyer Beetle, et al.
"These and other problems underscore the urgent need for the Arboretum and others to continue seeking new species for urban use," Kim says. The average lifespan of an urban tree is fewer than 10 years, according to Ware. But planting hardier trees increases the likelihood of a longer life span and a greener world - a goal that has never been more important than now, with climate change upon us."
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Family Ulmaceae - Zelkovas, Hackberries and Elms
There are about 200 species of trees and shrubs in Ulmaceae. Elms fell victim to Dutch Elm disease during the 1950s; until that time, they were the premier shade tree along the streets of our American towns and cities. The Morton Arboretum in past years has bred and marketed five new elm varieties resistant to Dutch elm disease.
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