Dutch elm disease-resistant elm trees
Dutch elm disease (DED) affects American elms (Ulmus americana), red elms (U. rubra) and rock elms (U. thomasii) throughout Minnesota. DED is one of the most widely-known tree diseases, worldwide. Fortunately, researchers have been working to breed and select DED-resistant trees to replace those stately giants. These trees are finding their way into home landscapes due to increased demand and nursery availability.
Since 1999, the University of Minnesota has been evaluating, selecting and screening elms for use in Minnesota. They have studied thousands of elms from many varieties. All trees listed below should be hardy in USDA Zone 4, unless otherwise noted.
Hybrid Asian elms
Hybrid Asian elms are the result of controlled breeding programs throughout North America. All have demonstrated resistance to Dutch elm disease and are great selections for tough sites where other trees won't grow. In general, hybrid elms are smaller at maturity than their American cousins. Many have leaves and mature forms that are distinctly different from American elms.
Accolade™ – Smaller at maturity but similar to the typical American elm form. Strong resistance to insects such as elm leaf beetle. Widely available at most nurseries and garden centers.
Cathedral – Vase-like shape, with good resistance to elm leaf beetle and other leaf cutting insects. Requires regular pruning during the first 15 years to develop a sound structure.
Discovery – Very slow-growing and smaller in stature than other elms. Winter hardy to USDA Zone 3, as well as stress and drought tolerant.
Triumph™ – More upright in form than Accolade, but slightly less insect resistance.
Commendation™ – Hybrid of Accolade, Siberian elm, and the European field elm (U. minor). Excellent form when young with interesting bark texture. Limited availability.
Danada Charm™ – Fast growing upright hybrid. Lower maintenance than some other selections. Beautiful red-tinged new growth. Limited availability.
Over the last 100 years there have been dozens of American elm selections. Unfortunately, most did not survive the ravages of DED and have been lost and forgotten. The following selections have shown resistance to DED and continue to provide options for the high-canopy shade that American elms are known for.
All American elm selections require a significant investment in pruning during the first 15 years.
Princeton – Selected in 1922. Vigorous growth rate with very upright form. Available in most garden centers and also through mail-order.
Prairie Expedition – A 2004 North Dakota State University selection. Classic vase-shaped American elm with outstanding autumn gold color. Winter hardy to USDA zone 3.
New Harmony – A USDA selection that appears to have superior form when compared to Princeton and Valley Forge.
St. Croix – Selected by Mark Stennes from a massive parent tree in Afton, MN, this elm joins the ranks of Dutch elm disease-resistant elms with a Minnesota twist.
|Growth Rate||Zone||Insect Resistance||Form||Maintenance Requirements||Height||Crown Spread|
|Danada Charm™||v. fast||4||good||vase||moderate||45||30|
|Cathedral||v. fast||4||good||vase||very high||45||30|
|New Horizon||v. fast||4||fair||upright||high||45||30|
|St. Croix||v. fast||4||good||wide vase||very high||40||30|
|Valley Forge||v. fast||4||fair||vase||very high||45||30|
1Height and spread dimensions are growth estimates in a typical 30-year timeframe. This incorporates knowledge of mature specimens, where available. Some dimensions are estimated and will vary greatly and may be influenced by site conditions and maintenance, especially pruning.
2Insect resistance recommendations are based on observations at the University of Minnesota, the Morton Arboretum and previously published works.
Where to purchase elms
Elms are gaining popularity and many nurseries grow and sell these varieties. Check with your local garden center and ask if they can special order your favorite elm if not currently in-stock. Many American elms are also available online.
Many of these elms require considerably more pruning and training than other landscape trees, and the first 15 years often determine how they will perform for the remainder of their lives. In the case of elms, a small investment in maintenance during the "formative years" will have a huge payoff when they are approaching maturity.
Like most trees, these elms are best maintained with a strong central leader (where small limbs are pruned and the main trunk is allowed to grow tall). This ensures a straight stem and keeps the tree growing up rather than out. As the lower side branches grow and increase in diameter, they should be removed until the desired clearance for the site is reached.
Knowing when and how much to prune and maintain trees requires experience, so if you are not sure how to work on young elms, contact an experienced tree care professional to get you started right. The investment made now will pay off when your tree is growing beautifully, is structurally strong, and is providing shade on your property.
Plant different varieties of trees in your landscape to help create a sustainable ecosystem. All of the elm varieties mentioned above offer excellent potential for use in rural windbreaks. These DED-resistant elms add to the array of tree species that can be planted in the upper Midwest, contributing to greener and cooler communities throughout Minnesota.
Jeff Gillman, formerly of UM Horticulture, St. Paul; Chad Giblin, UM Forest Resources, St. Paul; Gary Johnson/Eli Sagor, UM Forest Resources Extension, St. Paul; Mike Reichenbach, UM Extension, Cloquet; Gary Wyatt, UM Extension, Mankato; Kris Bachtell, Morton Arboretum, Lisle, IL
Reviewed in 2019