Developing Dutch-elm resistant trees

photograph of rows of young elm trees in the fall

Elm tree nursery at UMN Twin Cities, St. Paul

Photo by John Schoolmeesters


Dutch elm disease (DED) is one of the most critical invasive pathogens in Minnesota. Caused by the fungus Ophiostoma novo-ulmi, it has decimated the American elm in urban Minnesota, a tree known for its elegant form, full canopy, and winter hardiness. As cities also contend with the widespread loss of ash trees to emerald ash borer, there is a need for new trees to fill the gap. 

Researchers have been studying surviving elm trees in the region with the goal of understanding their natural resistance to DED. 

Research questions

  • What elm trees are disease-resistant?
  • How can we best propagate resistant elms?
  • What are the best methods to reintroduce resistant elms to the Minnesota landscape?


Held and his team have identified, propagated, and tested survivor elms from the Minnesota landscape, with some initially showing resistance to Dutch elm disease. They identified 23 new survivor American elm trees and propagated them for future testing. 

From the 23 trees, they made 300 grafts to be used for future inoculation studies. They also made over 200 grafts that were planted in parks and natural areas. This includes Nerstrand Woods, Elm Creek Park Reserve, and Izaak Walton League in the Mississippi River Valley.

In addition, they screened by inoculation studies 15 elm selections from prior years. These showed very good to partial resistance in most selections.


  • Planting event with the Green Crew of Izaak Walton League - Minnesota Valley Chapter, 2023
  • Urban Forestry Outreach and Research Community Forestry Field Day, 2022
  • Northern Green Expo, 2022
  • Upper Midwest Invasive Species Conference, 2020

News and media

Report a mature, surviving elm

If you know of an elm tree that may have survived Dutch elm disease, please let us know. 

Report a surviving elm


Research team

Benjamin Held | co-principal investigator

Ryan Murphy | research fellow

Gary Johnson | cooperator

Robert Blanchette | cooperator


Lab or other website

Urban Forestry Nursery & Lab: Dutch Elm Disease


Collaborating organizations

Minnesota Landscape Arboretum

Minnesota Department of Natural Resources

Minnesota State Parks

Minnesota Department of Agriculture

Minneapolis Park & Recreation Board

City of Saint Paul

City of Duluth and other municipalities

Three Rivers Park District

Green Crew of the Izaak Walton League - Minnesota Valley Chapter

MN Society of American Foresters