Cold Tolerance of American Elm

Research Issue

Field collection of American elm current-year shoots for cold tolerance assessments in the laboratory. Photo credit: Paula Murakami, US Forest Service.

American elm, Ulmus americana, was widely distributed throughout the eastern United States before the arrival of Dutch elm disease (DED), caused by the fungi Ophiostoma ulmi and O. novo-ulmi. Today, scientists are identifying and breeding DED-tolerant varieties of American elm so that the species can be restored in forests and cities.

Although vulnerability to DED is the biggest obstacle to American elm restoration, the new varieties must also be capable of surviving other stresses. An important factor that limits an individual tree’s survival and growth in northern latitudes is tolerance of cold temperatures.

Our Research

Scientists at the Northern Research Station have a large-scale program to identify and breed genetically diverse populations of American elms that are DED-tolerant. We are also testing individual trees to see if American elm clones being assessed for restoration in the north are cold tolerant enough to survive periods of extremely low temperatures. American elm restoration in New England and the upper Midwest includes locations where winter temperatures can go below -30° F (-34.4°C). We are studying how cold tolerance is affected by different genetic and site factors such as: 1) the genetic source of DED tolerance; 2) breeding with elms from locally cold-adapted populations; and 3) low temperature exposure associated with season and planting location.

Case study: Forest Service scientists began restoring American elms on the Chippewa National Forest (CNF) in northern Minnesota in 2007. In hardwood forests and riparian ecosystems on the CNF, American elm has been greatly reduced or eliminated by Dutch elm disease. A few American elm cultivars possessing natural tolerance to DED have been identified and reproduced; however, these cultivars likely do not have the necessary level of cold tolerance to survive on the CNF. To address this issue and to increase the genetic variability of trees used for restoration, we are working to produce trees with both cold tolerance and DED tolerance that can survive and prosper on the CNF.

Expected Outcomes

Identification of American elm families that are DED tolerant and cold tolerant enough for restoration in the species’ northern range.

Research Results

Knight, Kathleen S.; Haugen, Linda M.; Pinchot, Cornelia C.; Schaberg, Paul G.; Slavicek, James M. 2017. American elm (Ulmus americana) in restoration plantings: a review. In: Pinchot, Cornelia C.; Knight, Kathleen S.; Haugen, Linda M.; Flower, Charles E.; Slavicek, James M., eds. Proceedings of the American elm restoration workshop 2016; 2016 October 25-27; Lewis Center, OH. Gen. Tech. Rep. NRS-P-174. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 133-140.

Slavicek, James M.; Baggett, Kelly; Swanson, Gary. 2009. Restoration of the American elm on the Chippewa National Forest through generation of Dutch elm disease tolerant, cold-hardy, and site-adapted trees. In: McManus, K.A.; Gottschalk, K.W., eds. Proceedings, 20th U.S. Department of Agriculture Interagency Research Forum on Invasive Species, 2009. Gen. Tech. Rep. NRS-P-51. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 95.

Research Participants

Principal Investigator

  • Paul G. Schaberg, US Forest Service, Northern Research Station, Research Plant Physiologist

Research Partners

  • Last modified: May 6, 2019