The Largest Elm Tree Restoration Effort in the Northeast
Thousands of experimental trees are poised to help us bring back this iconic species.
The majestic American elm (Ulmus americana) was once the biggest and longest-lived tree on our northern floodplains. They held a unique and critical niche that no other floodplain tree has been able to fill since their precipitous demise in the 1970s.
Our dogged focus on American elms is rooted in our initiative to restore floodplain natural communities, a key natural climate solution to improving water and air quality, increasing flood resiliency and providing critical habitat for wildlife. Bringing back this lost tree species is a story about an innovative, science-based approach to restoration and the lands and the people who manage them.
In the face of severe climate change events and increasing biodiversity loss, our natural areas are platforms from which The Nature Conservancy can respond to the region’s most pressing threats and most exciting opportunities. As other tree species face invasive pests and disease, the restoration lessons literally seeded with our American elm project may inform other rescue efforts in the future.
The Many Gifts of the American Elm
The roots of the American elm are mighty. They can be submerged in floodwater for days. They naturally filter sediment while also tempering the impacts of flood events. Their trunks can withstand the impacts of bashing from spring storms and ice-melt, making elms an important part of floodplain forests. Large mature elms once grew taller than other floodplain tree species and provided important habitat for eagles, ospreys, barred owls, a host of breeding songbirds and mammals such as roosting bats and flying squirrels.
Planting for the Future in Vermont
Sadly, American elms today are diminished from their former glory as the biggest, oldest trees along our rivers and gracing our Elm Streets—more than 30,000 American streets bear the name "Elm." What caused their fall? The disastrous Dutch elm disease felled an estimated 77 million American elms in the 1970s.
To restore American elms to their former importance on our floodplains, TNC is working with the United States Forest Service (USFS) to develop a genetically diverse population of elms that are Dutch elm disease tolerant. TNC Ecologist Dr. Christian Marks formerly began developing new strains of elms which are being planted by the tens of thousands throughout the Connecticut River region, making it the largest elm restoration effort in the northeast. Today, nearly a decade later, TNC’s Senior Conservation Planner Gus Goodwin continues to manage the project and monitor the trial sites through its third round of funding.
A Living Laboratory
Since 2014, we have worked alongside the USFS to plant more than 10,000 American elms in floodplain forests across New England. The vast majority of these trees are experimental crosses between wild surviving elms identified by TNC in New England and elms that have already been rigorously tested by the USFS for disease tolerance. The plantings, which are primarily in Vermont, are part of a larger research effort led by the USFS and complement extensive research plantings in Ohio and Wisconsin.
Listen to our elm story on Vermont Public Radio.
Planting and caring for these disease-resistant American elms is no easy feat, requiring upwards of 140 persons and days per year to prune, tag, measure, fertilize and monitor the trees, and to manage competing vegetation within the planting site. Visit one of our elm plantings at Hubbardton River Clayplain Natural Area in Benson, and you would find nearly 6,000 8-foot-high saplings marked with metal identification tags tracing their origins.
Gus out in the field.
While the goal in the years to come is to witness an emerging floodplain forest come to life with a genetically diverse array of American elms, the site for now is truly a living laboratory where research and experiments of all forms are taking place: the passing on of disease resistance, natural environment impacts on restoration sites and improving transplanting success. In 2026, the final stage of this important work to bring back a species will result in each tree being inoculated or treated with a direct stem injection of the Dutch-elm fungus as the ultimate test of survivorship.
Senior Conservation Planner Gus Goodwin has been involved with the elm project since his early tenure at TNC. He has been in charge of collaborating with different partners across the network to work together on various stages of the project. The project is currently on its third round of funding, with a hopeful innoculation stage in the upcoming years. Below find some of the most commonly asked questions about elm trees and how you can take part in this ongoing project.
FAQ: All About Elms
-
With a little practice, elms are easy to identify. They have a lovely vase-shaped form, toothed leaves with an asymmetric swelling at the base, and their winter buds point away from the branch at a jaunty angle. There are several great resources available to help you train your eye and confirm your identification. Seek App (available for your smartphone) is helpful for getting close; confirm using Go Botany, a wonderful resource shared by the Native Plant Trust, that has a nice elm page. One additional tip for distinguishing slippery elm (an uncommon elm) from American elm is to look at a chunk of bark. When broken in half, the bark of slippery elm will be red throughout, while American elm will have bands of red and white, like a ham and cheese sandwich.
-
In our elm breeding program, we look for trees that are old and that we know have survived exposure to Dutch elm disease. We do this for a few reasons. First, young elms are generally tolerant of the disease and only succumb to it in their middle age (50+ years). Second, because the disease is spread by beetles with a short flight radius between host trees, it is possible for elms that are isolated from other trees (~300ft) to reach a mature status without actually ever having been exposed to the disease. We call these trees “escapers” rather than “survivors.” To make sure we only included survivors in our breeding program, we screened trees with the criteria of ~3-ft diameter at breast height, never treated and within 300 feet of recently infected elms. If this sounds like your tree, you should report it to the USFS, which has a web portal for tracking surviving elms.
-
You can plant some of the DED-tolerant elms that can be found at your local tree and shrub nursery. If you have the space, try to get several different varieties of disease-tolerant elm. This allows you to spread out risk, introducing more genetic diversity and creating a buffer against some poorly understood factors that create a range of disease tolerance, even among genetically identical individuals. For our restoration out-plantings, we used 25 trees with five trees of different varieties (e.g., Princeton or St. Croix). Planting a variety also allows the trees to cross-pollinate, creating offspring with novel genetic combinations that could also have elevated tolerance.
You might also consider planting the trees with non-elms in between to keep your elms from root grafting. There are experiments underway to confirm the necessity of this practice, but there is concern that the mechanism that confers disease tolerance when exposed to the DED pathogen through stem-injection (by beetles or humans) will not protect against transmission of the pathogen through root grafts. The final thing to consider is the cold-hardiness of your selected varieties. Trees from the mid-Atlantic or Midwest can be vulnerable to winter injury.
-
Yes, unfortunately. Here in the northeast, our forests have been especially hard hit by invasive forest pests and pathogens. Chestnut has been virtually eliminated, and several species, including ash, hemlock and beech, now risk a similar fate due to recently introduced pests and pathogens. Many organizations, including the USFS and TNC, are working on breeding resistant trees in each of these species, but so much additional work must continue if we want our forests to be diverse and healthy in the coming century. We need to adopt policies to limit new introductions, invest in research for controlling the severity of pest outbreaks (such as biocontrol agents), continue breeding resistant trees and attend to the stresses that make our trees more vulnerable to pests and pathogens.
We Can’t Save Nature Without You
Sign up to receive monthly conservation news and updates from Vermont. Get a preview of Vermont's Nature News email.
