ST. PAUL, Minn. — Throughout the state, Minnesotans are still noticing native American elms falling prey to Dutch Elm Disease (DED). DED is one of the most widely known tree diseases, affecting elms worldwide. Fortunately, dedicated researchers have been working to breed and select DED-resistant trees to replace those stately giants.
DED was first isolated in the Netherlands in 1920, hence the name, and by 1930, it was discovered in Cleveland and Cincinnati, Ohio. The first confirmed case in Minnesota was recorded in 1961 and by the late 1970s municipalities statewide lost massive portions of their urban forests to the disease.
Since 1999, the University of Minnesota has been cooperating with the Minneapolis Park and Recreation Board to evaluate and select elms for use in Minnesota. To date, they have studied more than 1,000 elms from over 30 different varieties, many of which are now readily available to the general public. Some of these elm selections are available at your local garden center, while others are available only via mail order. Unless stated differently, all trees listed below should be hardy in USDA Hardiness Zone 4.
Hybrid Asian Elms
• Accolade™ – smaller at maturity but similar to the American elm, excellent winter hardiness and strong insect resistance
• Cathedral – vase-like shape, good resistance to elm leaf beetle and other leaf cutting insects, leaf hoppers and similar pests however can be a problem and may require control practices
• Discovery – very slow growing, requires crown thinning to avoid cross branches, winter hardy to Zone 3, stress and drought tolerant
• Triumph™ – more upright in form than Accolade, but slightly less insect resistance, excellent winter hardiness in the Twin Cities
American Elms
• Princeton – selected in 1922, vigorous growth rate, upright form, available in some garden centers and also through mail order
• American Liberty – cloned from 6 different parent trees, variable growth rate, available through mail-order only
• Valley Forge – USDA selection, outstanding DED resistance, requires heavy pruning, limited availability through mail-order
A simple Internet search, including the variety name, should provide mail-order sources for many of these selections.
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http://www.extension.umn.edu/extensionnews/2009/dutch-elm-disease.html
Contact:
Catherine Dehdashti, (612) 625-0237, ced@umn.edu
