Tree Crops
Trees as the next harvest
Description
In the 1910s and 1920s, a geographer named Russell J. Smith spent years walking eroded hillsides across the American South, the Mediterranean basin, and the terraced valleys of China and Corsica. What he saw in the United States alarmed him: rain stripping topsoil off ploughed slopes, gullies opening where corn had grown a season earlier, whole farms sliding downhill one storm at a time. What he saw in older parts of the world offered a contrast that stuck with him. On steep ground where a plough would have been a disaster, people had planted chestnuts, carobs, olives, and mulberries — and were still harvesting food, generation after generation, from land that had never been torn open.
Out of that contrast came a book. Smith published Tree Crops: A Permanent Agriculture in 1929, and revised it a few years before his death in the 1950s. Its argument was blunt for its time and remains uncomfortable now: the plough, applied to hilly land, is a slow catastrophe. Annual crops leave soil bare and exposed for months a year, and on any slope that means erosion. Smith's alternative was not to abandon farming but to change what the farm was made of — to put trees to work as producers of food and feed, not merely as timber or shade.
He called it permanent agriculture, and he meant permanent literally: a system that could hold the same ground productive for a hundred years or more. Nearly a century later, as agroforestry, carbon farming, and food security move back to the centre of the conversation, Smith reads less like a forgotten agronomist and more like someone who saw the whole problem early. His book asks us to reconsider what a crop even is.
The question we’re asking : What if the harvest we keep looking for isn't in the ground each spring, but standing in the field year-round as a tree?What we’ll see : How a geographer turned soil erosion into an argument for farming with trees — and what it would mean to treat land as a century-long investment rather than a seasonal one.
Table of contents
01Chapter 1 — The hillside that washed away
Smith's book opens not with a theory but with a wound. He had watched American farmers push corn, cotton, and wheat onto slopes that had no business being ploughed, and he had watched the consequences arrive with every heavy rain. The soil that took millennia to build ran off in a single season. Gullies deepened until fields split in two. Smith described farms where the productive layer was simply gone, leaving subsoil and stone where a family had once grown its living. To him this wasn't bad luck or bad weather. It was the predictable result of a method — the annual, clean-tilled row crop — used on ground it was never suited for.
The mechanism is almost embarrassingly simple. A ploughed field spends much of the year as bare, loosened earth. Rain lands on nothing that holds it, so it runs downhill, and it carries the finest, richest particles with it. On flat land the damage is slow. On a slope it is fast and often irreversible within a working lifetime. Smith calculated the losses not in poetic terms but in inches of soil and tons per acre, and the numbers were grim enough that he treated erosion as a national emergency long before the Dust Bowl made the point for him.
02Chapter 2 — Trees that feed as well as fields
The obvious objection to farming with trees is that trees give us wood, fruit, and nuts for people — not the bulk calories and animal feed that agriculture actually runs on. Smith spent much of his book dismantling that assumption. His central insight was that certain trees are, in effect, standing grain and forage crops. The chestnut, he pointed out, had fed whole regions of Europe for centuries as a staple starch, ground into flour and eaten as bread. The carob pod, sweet and protein-rich, was excellent livestock feed. The honey locust, the oak, the mulberry, the persimmon, the pecan — each could pour out a heavy annual yield of food or fodder from land that no plough would ever touch.
He gathered these examples with the patience of a naturalist building a case. Across the book he catalogues species from around the world, weighing their yields, their hardiness, their uses, and their suitability for different soils and climates. The point was not nostalgia for peasant orchards. It was a working proposal: that a well-chosen tree crop could match or beat an annual field crop in food produced per acre, while doing none of the damage. A honey locust dropping bushels of sugary pods, or an oak selected for sweet, low-tannin acorns, could feed cattle and hogs directly, turning a hillside into a pasture with a roof.
03Chapter 3 — The permanent partnership underground
Smith's argument runs deeper than yield tables, because trees do something in the ground that annual crops cannot. Their roots reach far below the reach of any plough, drawing up water and minerals from depths that shallow-rooted grain never touches. That deep architecture is what lets a tree hold a hillside together and keep drawing on the soil through a drought that would flatten a corn field. Where an annual crop lives on the thin surface layer and depends on it staying put, a tree treats the whole profile of the soil as its territory.
This is where his idea of permanence becomes literal rather than rhetorical. A field of trees is a living structure that improves the ground it stands on year after year. Leaves fall and rot into humus. Roots open channels that let rain soak in instead of running off. The canopy shades and cools the soil, holding moisture that a bare field would lose to the sun. Over time, Smith argued, land under tree crops does not degrade the way ploughed land does — it accumulates. The farm becomes an asset that compounds instead of an account that is drawn down.
04Chapter 4 — Farming for a century, not a season
Step back from the chestnuts and carobs and Smith's book is really an argument about time. Conventional agriculture measures itself in seasons: this year's yield, this year's price, this year's decision to plant. It is an economics of extraction, taking what the land gives now and hoping there is enough left for next spring. Tree crops force a different clock. A nut tree planted today may not carry a full harvest for years, and may then produce for a century. To farm that way is to accept that the return on your labour arrives long after the work, and keeps arriving long after you are gone.
That shift in horizon changes what counts as a good decision. Under the annual frame, leaving soil to erode is almost rational — the cost lands in a future the current season doesn't have to pay for. Under Smith's frame, the land is a hundred-year asset, and destroying it to squeeze out one more crop is obvious folly. His permanent agriculture is, at bottom, a proposal to lengthen the memory of farming, to make the farmer accountable to the ground the way an owner is accountable to a building they intend to leave standing.
05Conclusion
Smith began by looking at ruined hillsides and asking why some land had lasted and some had not. His answer, laid out across Tree Crops, was that permanence in farming is not a matter of luck but of design — and that the design already existed in the chestnut groves and carob orchards of older countries. The plough, on sloping ground, mines the soil. The tree, rooted deep and covering the earth year-round, holds and even builds it, while still delivering a harvest of food and feed.