American Elm - Ulmus americanus
Family Ulmaceae - Zelkova, Hackberry, Elm

American Elm suffered a dramatic decline in the 1950s with the epidemic of Dutch elm disease.
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American Elms
Morton Arboretum accessions 604-25*1, 2 & 3, are from grafts done 83 years ago.
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.

American Elm autumn colors
This huge American Elm near the arboretum's headquarters is about 80 feet tall
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."[2]

American Elm trio
This native North American tree grows quickly when young, forming a broad or upright, vase-shaped silhouette, 80 to 100 feet high and 60 to 120 feet wide. Trunks on older trees could reach to seven feet across. The deciduous leaves are dark green throughout the year, fading to yellow before dropping in fall. In early spring, before the new leaves unfold, the rather inconspicuous green flowers appear on pendulous stalks. These blooms are followed by green, wafer-like seedpods which mature soon after flowering is finished. The seeds are quite popular with both birds and wildlife.
American Elms in fall colors
Here are our three girls in glorious yellow autumn colors.

When I was a child in the 1950s, my street in Des Plaines, Illinois, was lined with huge elms. We walked to school shaded by those magnificent trees; they were so tall their branches overarched the street completely. It was a wonderful walk then, and especially in fall when our mornings were bathed in yellow light filtering through the glorious butter yellow foliage.

But when the school year started in 1960, those trees had all been cut down, victims of Dutch Elm Disease. It was so sad, and now we walked under blazing sun and boy, did we miss those trees. Similar scenarios are now playing themselves out amongst the lodgepole pine and ash trees of North America. Nature green in tooth & claw, so to speak.

References
  1. American Elm, Morton Arboretum accessions photos: Bruce Marlin
  2. The Morton Arboretum, Arboretum Records Honor, Milestone; Looks to Future, http://www.mortonarb.org/res/GEORGEWARE.pdf
Tree Encyclopedia / North American Insects & Spiders is dedicated to providing scientific and educational resources for our users through use of large images and macro photographs of flora and fauna.
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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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