More of a 2.5. It's a breezy little read written in that non-committal sappy way of human interest stories, which is fine if that's you're looking for in the book, but there's something poorly aged about that angle only 13 years after this book was published in 2007.
I. Symbolism
Take the title. It's not clear what's "perfect" about the American chestnut. What does it mean for a thing which exists to be perfect? Wouldn't that imply no need for change? But that's exactly the problem with the tree - it couldn't survive change. Or is it perfect because it represents America? In that case, if the Chestnut is a symbol of American purity, there are two issues.
1) The chestnut was a staple tree of the indigenous communities living in America prior to colonization. They go largely ignored by Freinkel except for a one-off reference at the very beginning, treated like they existed just to keep the seat warm for colonizers who they taught The Ways of the Chestnut. Those communities would be the true symbol of American purity then, not the idealized Appalachia of the 20th century, and it would be important to have their voices included in the history of the American Chestnut. Of course this is not that. It's a history of America in a chestnut. Which brings me to
2) It becomes increasingly uncomfortable to think about the implication that American purity (here translated as white landowners) was ruined by foreign agents in the form of the Chestnut Blight, and that a rigid program of genetic re-culturing was necessary to protect against this invasion and preserve the species. I'm not saying this was Freinkel's intention. It's hard to unsee the implications of this aesthetic choice however, and if you don't see the problem with this narrative of (white) American exceptionalism carved into a "perfect" tree I don't know what to tell you.
II. Material
Freinkel doesn't have a systematic critique of the forces at work in American Chestnut. She wants to be an environmentalist and against exploitation, it seems, but when you can only count trees as $ it's hard to stand firmly in favor of the environment. Hence why when she circles back on the cause of the loss of the American chestnut she's prone to primarily focus on historical globalist reason (for lack of a better term): international trade pre-genetics and committed forestry. It's why when mentioning the harms of surface mining on the environment she couches it in the legal requirement of mine operators to restore/remediate land they work on at cost.
What goes generally avoided (although she mentions in passing twice) is that it was the indiscriminate panicked rush to massacre the existing American chestnuts before they lost their economic value that likely had a heavy hand in their decimation. What is glossed over is that the federal law that mandates mine operators to restore land is functionally a trust system where states have primacy of oversight, effectively making it fangless, especially in regions where mining companies are the political power brokers. What must be deduced from these blind spots is that Freinkel is a sentimentalist for a dying species without a clear vision of the system that has been killing it. This book is best suited for one of those 5 Minutes of Hope spotlights that news stations loves to dispense as medicine for the jump scares they call coverage but which is actually ad revenue.
Overall
As something other than the quirky collection of a dozen technocrats, hard-nosed scientists, and fiscally-driven organizers, American Chestnuts fails to make a point. It takes less than a second to notice that the introduction begins by saying that "those that did bear witness to the tree's disappearance...were the rural poor" before introducing the first voice of the book as "the late Barney Barnhart, a wealthy Pennsylvanian businessman" who seems to embody the kind of privileged "chestnuttiness" that the book is interested in noticing. Not Others, the unheard. Not the vitality of the tree itself. Not its function in culture, society or economy - beyond the occasional price tag. Ironically, not even the way in which capitalism hampers the ability of researchers to research ways to preserve the species except towards future profits for paper/pulp companies: The Institute of Forest Biosciences Freinkel mentions in chapter 8 closed in 2019.
It points to a well-meant but uncritical trivia whose most engaging character almost encapsulates the spirit of this book. William Murrill was the first scientist to catalogue the Chestnut Blight and would use it as a pin in his cap when writing his congratulatory third-person autobiography despite being "remarkably unsentimental about the plight of the chestnut." It's pleasant, but its pleasantness feels like complacency. It's a grand shrug. I'm not sure what else could have been expected in as politically unconscious a time as 2007 though. What would this book have been in 2020, I wonder?