To that end, he said he planned to use the nuts Powell gave him to make chestnut pudding and oil. He would take the dishes to the Onondaga territory and invite people to rediscover their ancient flavors. “Hopefully,” he said, “it will be like greeting an old friend. You just pick up right where you left off.”

The $3.2 million gift from the Templeton World Charity Foundation in January should keep Powell going as he navigates the regulatory bureaucracy and expands his focus from genetics to actual restoration across the landscape. If the government gives its blessing to his tree, Powell and American Chestnut Foundation scientists will begin allowing it to flower openly. The pollen, with its extra gene, would blow — or be brushed — onto the waiting receptacles of other trees, and transgenic chestnut destiny would unfold independently of controlled experimental settings. Assuming the gene holds up in the field as well as it does in the lab, which is no certainty, it will spread outward through the forest — an ecological point of no return that scientists long for and activists dread.

Once there’s a deregulated chestnut tree, will you be able to buy one? Yes, Newhouse says, that’s the plan. Already, the researchers are asked every week when trees will be available.

In the world that Powell, Newhouse and their colleagues inhabit, it’s easy to feel as if the entire country is waiting for their tree. But a short drive north from the research farm, through gritty downtown Syracuse, is a reminder of how profoundly both the environment and society have transformed since the American chestnut disappeared. Chestnut Heights Drive, in a town just north of Syracuse, is an unremarkable residential street with wide driveways, neat lawns and the occasional small ornamental tree dotting front yards. Timber companies are not asking for a revived chestnut. The subsistence-farming economy that was built on chestnuts is entirely gone. Almost no one has experience extracting the soft, sweet nut from the imposing burr. Most people are probably not even aware that anything is missing from the forest.

I stopped to eat a picnic dinner by Onondaga Lake, in the shade of a large white ash tree. The tree was infested by emerald ash borers; I could see the holes the insects made in the bark. It was starting to lose leaves and would probably, in a few years, die and crumble. Just to get here from my home in Maryland, I had driven past thousands of dead ash trees, bare pitchfork-shaped branches rising beside the road.

In Appalachia, companies have scraped the trees from an area larger than Delaware, to gain access to the coal beneath. The heart of coal country happens to overlap the heart of what was once chestnut country. The American Chestnut Foundation has partnered with organizations that plant trees on abandoned coal mines, and chestnuts are now growing on thousands of acres of these devastated places. Those trees are only partly blight-resistant hybrids, but they could become the parents of a new generation of trees that will someday rival the forest giants of old.

Last May, the concentration of carbon dioxide in the atmosphere hit, for the first time in human history, 414.8 parts per million. The nonwater weight of the American chestnut, like other trees, is roughly half carbon. Few things you could plant on a piece of land would suck carbon out of the air faster than a growing chestnut tree. With this in mind, an essay last year in The Wall Street Journal suggested, “Let’s farm chestnuts again.”

The new chestnut will be birthed into an old, broken world. It will have its work cut out for it.