For decades, the Viles Arboretum in Augusta played a small part in one plan to bring back American chestnuts, the once-ubiquitous tree almost eliminated by blight. It was home to hybrid trees that scientists tried to cultivate with genes from Chinese chestnuts, which could survive the disease.
But the blight got those trees too. Now, the arboretum has made room for a new seed orchard. The seedlings to be planted there represent early steps in a new approach that could produce strong American chestnuts ready for widespread planting in about 15 years.
The Maine site is one of just a few supplying a multistate breeding program that aims to restore American chestnuts to eastern forests by using advanced technology to find the very hardiest trees to breed with each other for survival.
“It’s a very complicated genetic nut to crack, so to speak,” said Mark McCollough, president of the Maine chapter of the American Chestnut Foundation, which leads the breeding efforts.
If that nut is cracked as expected, it will mark a major, long-awaited step forward in the effort to bring back the trees, which once served key roles in ecosystems and for people from Georgia to Maine.
Before the blight arrived from overseas around 1904, American chestnuts were one of the most abundant species in regional forests.
Their nuts fed animals, their blooms were a major resource for pollinators each summer and the trees were a host plant for hundreds of moths and butterflies. For people, the trees provided abundant, nutritious food and versatile, rot-resistant lumber with so many uses it was called the “cradle to grave tree.”
“The [tree was] the foundation of the ecology of our eastern forest, and we’re missing that now,” McCollough said.
For decades, the national foundation’s breeding program focused on developing a chestnut that could tolerate blight by combining, or hybridizing, remaining American chestnuts with Chinese chestnuts or other Asian varieties. The trees produced were planted and shared along the way, and can be found across Maine today.
Scientists long believed two or three genes in the Chinese trees were responsible for their ability to tolerate blight, and that breeding could capture those genes and introduce them back into American trees.
Maine was involved in that effort, with the local chapter establishing more than a dozen orchards around the state. But in recent years, it became clear that the hybrid strain wasn’t as tolerant of the blight as earlier scientists thought it would be, according to McCollough.
At the same time, technology had evolved to allow scientists to map out the genomes of both varieties of chestnut trees. It found that instead of just two or three genes helping the Chinese chestnut tolerate blight, around 200 genetic regions were responsible across its 14 chromosomes.
The national organization eventually settled on a new strategy called recurrent genomic selection, an approach that’s used in selective breeding for complex traits in plants and animals, such as increasing crop yields or milk production.
A computer model selected the best-prepared trees out of more than 5,500 across their range. Those trees will be pollinated with each other and grown out into seedlings, exposed to the blight fungus as a test with the top survivors planted into seed orchards like the one in Augusta.
The process will be repeated until it creates a tree that has high enough blight tolerance to survive long-term in the wild.
The new technology will “greatly accelerate” the breeding process, and it’s possible a good candidate for planting in the forest could be created in about 15 years, according to McCollough.
The orchard at Viles Arboretum will be one of just a few seed orchards growing out the top 5% of the first couple of generations of the new trees. Twelve of the top trees came from Maine.
The chapter will also likely test plantings in other Maine settings, but the Augusta site will be its major contribution to the new program.
“That’s pretty special, that the Maine chapter and the Viles Arboretum can be a real important player in nurturing those chestnuts,” McCollough said.
Maine has other important roles to play in conservation efforts, too. It has more “legacy” trees, or large old American chestnuts that have survived the blight, than any other state.
Finding them, identifying them, and collecting their seeds is a key part of the Maine chapter’s work, according to McCollough. Those seeds are grown into seedlings the chapter sells to the public and donates to land trusts each year.
As part of that, the group started a program in 2025 called Chestnut Chasers, training volunteers to help find, revisit and document American chestnuts around the state.
Another initiative, Chestnuts Across Maine, started in 2024 to make small plantings in public settings such as at schools and land trusts to preserve genetics, build community, expand planting capacity, and to help reacquaint people with the trees. It aims to allow anyone to find a living tree by 2035 within an hour’s drive from their home or a 10-minute walk from a school.
The Maine chapter plans to plant 30 more sites this year and the program now has a waitlist, McCollough said.
He sees yet another unique role for Maine in the larger restoration project, too, because of the state’s position at the top of the tree’s traditional geographic range.
Climate change is already making conditions in Maine more favorable for the trees, which can now grow as far north as Fort Kent. If conditions also continue to get warmer in the South, within the next century Main could become an important place for the continued survival of chestnut trees.
In a November website posting, the Arboretum called the new orchard project a “promising step forward” as it made room for the new trees by clearing the plantings from 1981 that had succumbed to blight.
“This marks a meaningful moment for a project that has been taking shape here for more than four decades,” the organization wrote.
