A few years ago, a Philadelphia arborist named Max Paschall read an article about a man named John Hershey. Hershey ran a tree nursery and experimental farm in Pennsylvania in the 1930s. The article mentioned a food forest Hershey had planted, groves of carefully selected trees that were apparently still standing in a suburb of Philadelphia called Downingtown.

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“I thought, oh, that’s near me,” Max said.

And a few months later he made his way out there and was completely amazed by it. There were groves of trees sandwiched between a church parking lot and a daycare and a development with an apartment complex.

“It’s only when you kind of understand what you’re looking at that you realize that this is the oldest living agro-forestry system left in North America.”

Agro-forestry is the intentional integration of trees and shrubs into crop and animal farming systems. John Hershey was an early advocate—he saw agro-forestry as the way out of the environmental and economic horrors of the Dust Bowl years.

The trees he’d planted in the forgotten nursery are over 90 now, and incredibly productive, and Paschall started going back to explore the nursery regularly.

There are black walnuts, persimmons, paw-paws, hazelnuts, hickories, honey locusts, acorns, pecans, and hican trees—which is a hybrid of hickory and pecan.

“Pretty much anything that you can imagine that can grow here and that can survive for 80 years on its own—it’s all growing there, and it’s producing an enormous amount of food every single year,” Max said.

Surprisingly, Downingtown Pennsylvania is almost the exact same hardiness zone on a USDA climate map as Cape Cod—which means that in terms of temperatures, anything that can grow there can also grow here. And in fact, part of what’s so interesting about the trees Hershey planted is the way he sourced them from all over the eastern United States.

Hershey essentially did an early version of crowd sourcing. He worked for the TVA—the Tennessee Valley Authority—part of the New Deal in the 1930s.

During the Great Depression he was down in Tennessee working on their tree crops program. According to Max, he would put out advertisements in newspapers throughout the entire south every rural newspaper would have these ads that would say, ‘If you’ve got an amazing hickory nut or if you’ve got an amazing honey locust with sugary pods or if you have your favorite persimmon send it in to us and if you win the best of all the trees you’ll get a $50 reward.’

“He literally just crowd sourced the best genetics of all the trees that were still in existence at the time so he brought those back up to Pennsylvania and trialed them up here and found which ones produced the most reliably with the least maintenance and grew the most vigorously and so he kept the best of the best and that’s what essentially remains at his site,” Max said.

What’s left includes towering pecans, blight resistant grafted chestnuts, tannin-free edible acorns, sugary pod honey locusts, and thriving apples. And today, Paschall is doing similar work. He has his own nursery outside of Philadelphia where he’s trialing fruit and nut trees like hardy almonds, hazelnuts, and persimmons. Where Hershey was inspired by the Great Depression and the Dust Bowl, Pass Kull is working toward resilience in the face of a rapidly changing climate and shrinking wild spaces. He sees agro-forestry as having huge potential for the agriculture of the future.

“And so today you know people like me and people I work with are doing the same thing all over again, where we’re taking the cream of the crop from the people who came before us like John Hershey and J. Russell Smith and adding new things to it and seeing what really works.”

After I talked with Max, I dug up an old publication of John Hershey’s. It’s called Nature’s Orbits, Man’s Profits—put out in the 1950s—and it’s clear that long before the terms global warming and climate change became part of public awareness, Hershey saw where we were headed. He wrote: “Man in his progress of the last century nearly ruined the climatic balance by wrecking the forests and soils of this great and productive continent.” He offered his forty years experience in tree crops, he said, as a workable solution.