I know what you’re thinking…trees? Well, you can’t say I didn’t warn you, but, but! trust me, this is an exciting story. It is full of love and loss, loyalty and betrayal, perseverance and resilience. Does it have swords, you ask? How about pirates? Wellllllll…no. But it’s still a great story.
It begins right at the turn of the 20th century. At this time, the American chestnut tree (Castanea dentata) comprised up to 25% of eastern hardwood forests. Its domain stretched from Maine to Georgia (just like the Appalachian trail!). Some think that it would supplement the current nut mast (the amount of nuts available to animals in the forest) by 50-60%. This king of trees was not small: there are records of chestnut trees with diameters up to 21 feet (6.4 m) and heights of over 100 feet (~30 m). Thus, they were called the Redwood of the east.
Entire communities in Appalachia grew up around these trees. They used the hardy wood for furniture, log cabins, and fences. Structures built of chestnut wood are still standing today! They got tannins from the bark. They relied on the nuts as a staple. Humans weren’t the only animals to depend on these trees. Everything from bears to the now-extinct passenger pigeon relied on the chestnuts for sustenance.
But the early 20th century was also a time of Acclimatization societies (more on those later), and the global exchange of unique and interesting flora and fauna. The Chinese chestnut (Castanea mollissima) was just one among many introduced species at the time. Harmless by itself, the Chinese chestnut is a well-behaved orchard tree. It is short with a broad, aesthetically pleasing canopy, attractive leaves, and edible nuts. In contrast to its American cousin, it rarely grows taller than 30 feet or so (10 m).
It was the invisible companion of the Chinese chestnut that wreaked all sorts of havoc. The parasitic chestnut blight (Cryphonectria parasitica) traveled overseas along with its host. In the way of host parasite relationships all across the animal and plant kingdoms, the tree and fungus had a long history of coevolution: an arms race of defenses and offenses. As a result, the Chinese chestnut had strong mechanisms of resistance to the blight…and in the way of conquered peoples throughout history, the American chestnut succumbed in its susceptibility and naivite.
The Chestnut blight on agar culture. Also, a very famous chesnut scientist (Fred Hebard) in the background.
The rapidity with which the devastating blight spread across eastern North America was staggering. In just about thirty years after the first blight was recorded in New York City, the American chestnut was “ecologically extinct.” The great trees had been wiped from the face of the Earth in one fell blow.
The blight spreads through cracks in the bark, so there is even a great historical photo of a heart that someone has carved in the bark for their sweetie, with blight spreading out all around the cut. (I wish I could find that photo! If you have it, let me know.)
But the story doesn’t end there! Here’s the exciting part…American chestnuts are incredibly stubborn. Even over a hundred years after the death of their original crowns, the roots survive. And year after year, they send up shoots with tender green leaves to gather as many carbohydrates from the sun as they can before the blight strikes again and knocks them back into the ground. The ghost of this tree literally clings to life by its roots.
Those communities that had been built around the trees collapsed right along with them too. But humans, like trees, are also stubborn. Almost immediately upon observing the destruction of the blight, the USDA began a program to save the tree by breeding American chestnuts with Chinese chestnuts. The point was to get the resistance gene from the Chinese chestnut, but to maintain the features (ie stature, sweet nuts, growth habit) that made the American chestnut unique.
Pollinating a LSA, 80 feet high in a bucket truck with a pocket full of pollen.
That program is still running today, after a few hiccups due to misunderstandings about the inheritance of resistance. The American Chestnut Foundation still strives to create blight resistant American chestnuts. Among the root shoot survivors, there the very few LSAs (Large Surviving Americans) that produce flowers and nuts every year. A painstaking program of breeding and backcrossing has finally led to 15/16 American chestnuts that are blight resistant. The plan now is to plant them along the Appalachian trail, and to use them to reclaim abandoned mine sites.
An new orchard of resistant chestnuts...the future?
Now, I’m not saying that there aren’t some implications to this work. Lots of people have brought up questions of reintroducing this species. It is so dominant and grows so quickly, will it outcompete other native trees? The composition of our forests was so different before its demise, it is hard to imagine what would happen if we were to successfully restore it. Our efforts to “fix” something we have broken in nature have often turned out poorly, sometimes with disastrous results.
But it is a fascinating story, no? And it’s not over yet. It will be fifty years before we see the effects, even if they start planting resistant chestnuts now. So, next time you listen to that Christmas carol, think a bit about how humans have affected the world around us…think about how stubborn nature is, how resilient…and yet, how vulnerable.
PS. There was a chestnut anthology published if you want more info. It’s called “Mighty Giants.”