Article #73, July, 2003
By Bill Cook
Prior to the 1970s, the term “elm” evoked pleasant images of tree-lined avenues in America’s cities and towns. The word has likely lost this wonderful connotation and holds a place less dear in the hearts and minds of those too young to remember.
The Dutch elm disease wreaked havoc on our elm resource, killing millions of trees in cities and forests. Today, the elm resource is a fraction of what it was several decades ago and continues to lose ground.
This exotic disease affected primarily American elm, one of five Upper Peninsula representatives of the family Ulmaceae. The other species are less susceptible. Worldwide, there are 15 genera and about 150 species, mostly living in temperate regions. The Upper Peninsula is the northern margin for elms.
American elm is the best known member of the family and continues to be the most common, despite losses from the disease. It is the tallest of all the elms and frequents places of better soils and bottomlands. It can still be easily seen in fence rows. The spreading vase-like form makes identification from a distance easy. The hard wood had many utilitarian uses.
The slippery (or red) elm looks much like American elm, but is a smaller tree that prefers growing along the margins of wetlands and in floodplains. The inner bark feels gelatinous, giving rise to the name. Cross-sections of the bark reveal alternating brown and reddish layers. The other elms have brown and cream layers. Leaves have high levels of silicon creating a very scratchy feel. Some say that slippery elm leaves were used by pioneers as “brillo” pads.
Rock elm is usually a small to medium sized tree, growing along roadside ditches, although the species is not common. The corky growths on the twigs are distinctive. Neither rock nor slippery elm have the vase-like shape of the American elm.
Siberian elm was brought to the USA as an ornamental and because of its relative resistance to the Dutch elm disease. The leaves are elm-like, but quite small. Falling twigs provide an undesirable trait in an ornamental. All four elms have seeds encased in dry, oval, and flat cases, called samaras.
Hackberry is a member of the elm family but belongs in a genus different from the elms. The tree is rarely found outside Menominee County and is not common even there. The trunk bark has thick corky ridges, unlike any other tree. Fruits are small, dark purple “berries” with hard pits.
The elms are not the only trees to have been severely impacted by exotic pests. American chestnut, once the most common tree in eastern North America has largely been wiped out. Gypsy moth, adelgids, blister rust, leaf miner, oak wilt, and other exotic pests have affected many of our native tree species.
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Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at firstname.lastname@example.org or 906-786-1575.
by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005
J Road, Escanaba, MI 49829
906-786-1575 (voice), 906-786-9370 (fax), e-mail: email@example.com
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