The American chestnut tree spanned the eastern United States and numbered in the billions before blight wiped out most of the population. In this week’s episode, I’m sharing my personal affection for the American chestnut and speaking with an expert from The American Chestnut Foundation about what devastated this tree and what’s being done to save it.
Sara Fitzsimmons is the Director of Restoration for The American Chestnut Foundation, and an authority on all things chestnut tree. She studied forest ecology and management at Duke University’s Nicholas School of the Environment in North Carolina and joined The American Chestnut Foundation about 20 years ago as an intern. She is originally from southern West Virginia, but in her nearly two decades with the foundation, she’s worked out of Penn State University.
Her personal connection to the American chestnut predates her career. Sara recalls that her father, who was a teacher in Summers County, West Virginia, would salvage the wormy chestnut lumber from one-room schoolhouses that were torn down and then use the reclaimed lumber as paneling in their basement. He passed a love of chestnut trees to Sara, and that complemented her innate interest in pests, pathogens and forest health.
Sara says the American chestnut touched so many people’s lives because it was such a utilitarian species, and many members of the foundation, like herself, have familial ties to the tree.
Next to the American elm, the American chestnut is one of the first species that the United States lost to an exotic pathogen, Sara notes. Almost the entire species was fundamentally eradicated from the landscape, but with the work of the American Chestnut Foundation and others, that could be reversed.
The American Chestnut and Me
On last week’s episode of the podcast, I shared book recommendations, including one of my favorite books, Sally M. Walker’s “Champion: The Comeback Tale of the American Chestnut Tree.” This book fostered in me an interest in the ongoing efforts to save this tree.
I’m a guy who’s fascinated with trees in general. I can stand under a tree or near a tree for a long time, just in awe, imagining its life — because trees live for so long. I can’t recall exactly when I fell in love with the American chestnut tree, but I’m sure it was my first exposure to its remarkable story. The American chestnut has been called the giant panda of the forest world: You just love that bear the first time you see it, because what’s not to love?
In addition to the American chestnut’s history, scope, size and utility — every part of the tree, from its leaves and nuts to the rot-resistant wood itself is useful and valuable in some fashion — the tree is just gorgeous. The trees are believed to live 500 years or more and grow to be 200 feet tall, and the diameter can exceed 12 feet.
It was only recently that I saw an American chestnut tree in person, on a trip a few weeks ago to northern Tennessee, about 6 or 7 miles south of the Kentucky border. I was staying at a late-1700s trappers’ lodge that is now owned by the National Park Service. I learned that the main building was built with long pieces of wormy American chestnut wood, and a fellow guest informed me that there is a University of Tennesee American chestnut farm just 15 minutes away.
I was excited to go see 100-foot-tall majestic American chestnut trees, but it turned out to be about 40 to 50 scrawny trees, no taller than 40 feet, some with multiple trunks, some not. The fact is, the towering trees with 15-foot diameters that once numbered in the billions simply don’t exist anymore. It’s going to be a long and winding road to get back to where we were, and we’re not there yet, but we’re making great progress.
The American Chestnut Historically
American chestnut was renowned for its tall, straight trunk, its huge diameter and its rot resistance — traits that made it great for construction. The largest American chestnut on record was 17 feet in diameter.
Sara says the real “monsters” were found in Southern Appalachia, while trees did not get nearly as big in the north of the range, in Pennsylvania, New York and Massachusetts.
The tree was common in U.S. forests for 12,000 years, maybe longer, and spanned 180 million acres.
The Plight of the American Chestnut, and Efforts to Save It
The fungus that causes chestnut blight, Cryphonectria parasitica, was likely brought to the United States on imported Japanese chestnut stock from the mid to late 1800s. It was common then for nurseries in Pennsylvania, New Jersey and New York to sell Japanese chestnuts, because the trees are large and beautiful. Still today, 150-year-old Japanese chestnuts stand in botanical gardens in those states and elsewhere.
There were reports in the 1840s and 1850s of chestnuts mysteriously dying, and no one could pinpoint why. The fungus was finally isolated and identified in 1904, Sara explains, when forester Herman W. Merkel found cankers on trees on the grounds of the Bronx Zoo (then called New York Zoological Park) and named it “chestnut bark disease.” The fungus has two types of spores that travel on wind, water, animals, and people, so it traveled very quickly — about 20 to 50 miles per year.
Chestnut blight is a necrotroph, which is a type of parasite that kills its host before eating it. The fungus infects a tree then exudes an acid that kills the tree’s cells. Because the American chestnut has little to no resistance to the pathogen, chestnut blight can kill a tree fairly quickly.
In fewer than 50 years since Merkel’s discovery, an estimated 4 billion American chestnuts were wiped out, as efforts to combat the blight fell short.
In 1911, the governor of Pennsylvania set up the Chestnut Tree Blight Commission, which operated until 1914. That was the first concerted effort to try to stop the destruction of the American chestnut tree, and more efforts soon followed.
The U.S. Department of Agriculture sent Frank Meyer of Meyer lemon fame over to China to get Chinese chestnuts and bring them back to replace American chestnuts that were lost. Sara’s father ended up with Chinese chestnuts on their family farm through this effort, which spanned the eastern United States. The USDA cross-bred Chinese and American chestnuts and arranged tens of thousands of plantings, most of which have died out since then, though a few examples remain.
The Connecticut Agricultural Experiment Station did its own chestnut breeding in the 1950s and ’60s, and there were irradiation experiments in the ’60s as well. Unfortunately, none of those efforts worked.
The origins of The American Chestnut Foundation date back to 1983, when University of Minnesota corn geneticist Charles Burnham applied corn breeding techniques to chestnut trees. Burnham, along with David French, Don Wilkie and others got together and formed a nonprofit to try to restore the American chestnut.
Today, the American chestnut is classified as “critically endangered.” However, The American Chestnut Foundation calls the species “functionally extinct,” Sara says. One of the reasons trees hang on is because the fungus only kills the above-ground portion. Like with many hardwoods, chestnut tree roots will re-sprout from still-living roots. The trees live as long as they can, get reinfected, and then die back to the stump again, and repeat.
Down from billions, there are now roughly 431 million American chestnut trees that are living but infected by the blight or will become infected by the blight. Of those, 84% are less than 1 inch in diameter at breast height.
The Utility of the American Chestnut
While other tree species hold the titles of fastest-growing, tallest and biggest, the American chestnut scores highly in all three categories: It’s fast-growing, tall and massive. The trees can also produce nuts when they are as young as 5 years old.
The tree’s nuts, loved by people, were also a great source of food for wildlife — in some cases, making up more than 34 percent of a species’ diet. Because chestnut trees drop a similar abundance of nuts each year — unlike oak trees, which are more cyclical in the number of acorns they drop annually — chestnut trees are a more reliable source of food and nutrition for animals.
Deer, turkeys, passenger pigeons and Allegheny woodrats all saw their populations decline when the American chestnut declined. The passenger pigeon is now extinct — though other factors contributed to its extinction — while the Allegheny woodrat is classified as “near threatened” today.
Domesticated animals benefited too. In Southern Appalachia, ranchers would let loose their livestock to fatten up on the nuts.
Back when Sara started with the foundation 20 years ago, old-timers would tell her how they used to go out with a bucket or basket and fill it to the brim with chestnuts. It was common for New York City residents to go up to Connecticut just to collect chestnuts. It was called “chestnutting,” and it’s depicted in an 1870 wood etching by artist Winslow Homer.
The American chestnut has been called the “cradle to grave tree,” Sara says. Its lumber has been used for everything from cribs to coffins. Split rail fences still stand in Appalachia, and there is at least one utility pole made from an American chestnut that is still in use in Cape Cod. Inspection stamps on the pole indicate it goes back to the 1910s, and it continues to stand despite never being treated with preservatives.
The American chestnut was also revered by Thomas Jefferson, the Founding Father and president who was also a farmer and plant collector. Jefferson mentioned in a letter to George Washington that fences made from other lumber rotted out in less than a year, while chestnut wood fences stood firm.
It was also used for tannin extraction for the tanning industry before its decline. In fact, that was a panic in the 1950s before alternative sources were found.
Native Americans used the trunks for canoes and the leaves for medical purposes.
The Revival of the American Chestnut
There are a number of promising avenues being explored to repopulate the tree, and The American Chestnut Foundation is using all of them in concert.
Backcrossing and Inter-Breeding
One method is backcrossing, which begins with breeding an American chestnut with a Chinese chestnut, producing a hybrid. (The Chinese chestnut was chosen because it is naturally resistant to the chestnut blight.) That hybrid offspring is bred with an American chestnut, to produce a tree that is approximately 75% American chestnut. Continued crosses with American chestnuts down the generations yield trees that are more than 90 percent American chestnut — but the question is whether the remaining Chinese chestnut DNA carries the blight resistance trait.
The American Chestnut Foundation also practices inter-breeding, which breeds the most blight-resistant trees within each generation.
The foundation’s oldest moderately blight-resistant trees are on 12-year-old U.S. Forest Service plots, though improvements have been made since those were planted. It appears they can achieve resistance that is 75% to 80% as effective as Chinese chestnut’s resistance, but it’s unclear if that’s enough for restoration.
In 1989, the New York chapter of The American Chestnut Foundation started working with the State University of New York College of Environmental Science and Forestry on genetic engineering prospects as another avenue for restoration. However, there are regulatory hurdles that get in the way of conducting large-scale plantings to study. The USDA, the Environmental Protection Agency and the Food & Drug Administration all heavily regulate genetically modified organisms. To overcome such hurdles, the college has petitioned the USDA to grant non-regulated status to the genetically engineered American chestnut known as Darling 58, which has shown the greatest promise for producing new disease-resistant trees.
Another avenue of research that continues was first explored in the 1970s. It’s known as hypovirulence and involves a virus that infects the fungus, reducing the severity of chestnut blight and providing the infected tree an opportunity to fight off the blight.
When infected by the virus, the chestnut blight fungus turns white instead of its normal orange. To transfer the virus, white fungus is applied to the canker of a tree with chestnut blight. However, a tree must have some degree of innate blight resistance for hypovirulence to be effective.
The 3BUR Strategy
It was in 2014 that The American Chestnut Foundation adopted a strategy to marry all three techniques together, Sara says. It’s called Breeding, Biotechnology and Biocontrol United for Restoration, or 3BUR.
There’s also a separate foundation, the American Chestnut Cooperators’ Foundation, which is investigating why a couple of dozen trees, spread throughout the eastern United States, have an innate resistance to chestnut blight. That foundation has had some success breeding these large survivors together to produce resistant trees.
These large survivors are different from other American chestnut trees that have avoided infection through sheer luck. The survivors show signs of infection, with “cruddy bark,” Sara says.
There are already signs that efforts are paying off. Some insect species that were once abundant went undetected for decades after the American chestnut’s decline. Now that people are planting more chestnut trees, those insects are being found again.
Other Threats to American Chestnut
There are other threats as well, such as root rot affecting the southern end of the American chestnut’s range, and Asian chestnut gall wasps.
The chestnut root rot pathogen, which dies or goes dormant in the cold, is moving northward, due to climate change. Meanwhile, the tiny Asian chestnut gall wasps were introduced to the United States in the 1970s. While they do not kill trees, they do reduce the harvest, so they are a concern for commercial growers. Fortunately, a parasitoid wasp will appear after a couple of years of bad harvests, and kill off the gall wasps.
Spotted lanternfly, which is an invasive found in Pennsylvania and spreading, is another concern for American chestnuts. Then there’s the granulate Ambrosia beetle, which is native to Asia but now found in the United States. There are vegetative threats to forests as well, including mile-a-minute, kudzu, bittersweet and garlic mustard.
What Individuals Can Do
Renowned biologist, naturalist and writer E.O. Wilson says the restoration of the American Chestnut is inevitable. That’s very encouraging, and there’s even better news: You can help.
You can download the app TreeSnap, which was developed by the U.S. Forest Service and the University of Kentucky, to identify and tag the location of trees that are under attack, including American chestnut, ash, white oak, hemlock and American elm. The user takes pictures of a tree and its leaves and indicates if it appears to be one of the threatened tree species. An expert will review the photos to confirm if the tree is, in fact, a threatened species. The app asks other questions as well, such as the tree’s height, whether it is producing nuts and if it has blight.
They are interested in every threatened tree, from a sprout clump to a tree that’s producing nuts. However, nut-producing trees are of the most interest because someone can then come to the location to collect nuts and pollen or to pollinate the trees. The American Chestnut Foundation is also interested in areas where there are very few reports of American chestnuts, such as northern and central Mississippi, southern Ohio, southern Indiana, mid and western Tennessee and Kentucky — all places that, historically, were in the tree’s range.
When sprouts are found in locations of interest, someone from the foundation may come out to collect scionwood, which is a twig that can be grafted to rootstock elsewhere.
When The American Chestnut Foundation’s resistant trees are made available to the public, foundation members will have first dibs. Until then, Sara says the best thing individuals can do to help with restoration is to plant local-adapted wild-type American chestnuts. In the future, the foundation will diversify the genetically engineered Darling 58 by distributing Darling 58 pollen to members to apply to wild trees.
Nuts and seedlings are currently available to members for planting, but the foundation can’t guarantee chestnut blight resistance.
The End Goal
Sara says the end goal of The American Chestnut Foundation isn’t only the restoration of the species. It’s also to create a template and a framework to rescue other species that are under attack.
An important step is getting more people interested in the health of forests and to help them recognize why it’s important to have native trees and diversity in our forests. The more people are aware of what’s attacking our trees and threatening that diversity of native species, the closer we come to turning the tide against these challenges.
Do you have an American chestnut memory? Let us know in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
joegardener Online Gardening Academy™: Three popular courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting!
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
Petition to deregulate blight-tolerant Darling 58 (The deadline to sign or comment has passed, but the petition may still be viewed)
“Champion: The Comeback Tale of the American Chestnut Tree” by Sally M. Walker
Wild Alaskan Seafood Box – Our podcast episode sponsor and Brand Partner of joegardener.com – Enter code “Joe” at checkout for two special bonuses just for our podcast listeners – 2 pounds of Dungeness crab with your first order and free scallops for the life of your subscription.
*Disclosure: Some product links in this guide are affiliate links, which means we would get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us. None of the items included in this list have any bearing on any compensation being an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, Milorganite, Soil3, Exmark, and Wild Alaskan Seafood Box. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.