Osage Orange

Maclura pomifera


by Douglas Main, originally published in National Geographic November 23, 2021

The softball-sized fruits of the Osage orange may have evolved to be eaten by extinct megafauna, and their wood is ideal for making archery bows and warm fires.

When the fruits of the Osage orange tree fall to the ground in autumn, they demand notice. For one thing, they’re the size of softballs—the largest fruit of any tree native to North America. For another, they’re bright green.

On top of that they have a strange story that few people know.

Osage orange trees are not related to oranges; they’re more closely related to mulberries. Even more confusingly, the most common name for their fruit is hedge apple (though they’re also called horse apples, Irish snowballs, or monkey brains).

Not many animals or humans eat these neither-oranges-nor-apples. Though a couple animals, mainly squirrels, sometimes eat the seeds hidden inside the green flesh, they do not disperse them far. Some researchers think that the tree was once spread by extinct megafauna, perhaps giant ground sloths or mastodons, and that these fruits evolved to their ponderous size to appeal to these vanished giants.

More recently the Osage orange has managed to spread by appealing to humans. Take its wood, for example: It burns hotter than any other in North America, resists decay better than any other in the world, and is both flexible and incredibly strong. This rare combination makes it the world’s best wood for archery bows.

The tree also forms nigh impenetrable hedges, which made it a primary tool for settling the Midwest and Great Plains. The Osage orange has been the subject of national manias, presidential discussions, and scientific controversy. Queen Victoria is said to have tasted one of the glowing green fruits. She apparently didn’t like it much. But she may not have known its incredible backstory.

A strange miracle 

Today Osage orange trees are not uncommon, but they tend to be sparsely distributed, and seeing one is a treat. Or so I felt growing up in Champaign, Illinois, coming across a remarkable Osage orange with huge low-slung branches, perfect for climbing, in a city park. Like most kids I was drawn to the strange, fern-green fruits. They’re fun to hold, improbably large with a brain-like texture, and fun to throw. They also smell nice, somewhat floral, with hints of orange blossoms, pears, apples, and cloves.

Before the last Ice Age, the Osage orange had a vast distribution, from Florida north to Ontario. But then, starting around 125,000 years ago, glaciers advanced south to cover much of North America. Once the glaciers retreated around 12,000 years ago, the Osage orange did not quickly re-expand to the north like many other tree species—and in fact may have continued to shrink in range.

Before Europeans arrived, large populations of the tree were mostly restricted to portions of Arkansas, Oklahoma, and Texas, and possibly small parts of Kansas, Louisiana, and Missouri. Pre-settlement trees have also been found in Kentucky, Tennessee, and Virginia, says Tom Kimmerer, an independent forest scientist, consultant, and author based in Lexington, Kentucky.

Native Americans valued the plant highly and used it for archery bows and war clubs. And for good reason—as the U.S. Department of Agriculture notes, Osage orange has the highest work to maximum load value of any wood by far, meaning it has the rare combination of strength and flexibility. According to one early 19th century account, one bow would set you back a horse and a blanket.

The wood is also extremely resistant to decay and has the highest heating value of any native species, making it an ideal firewood. It’s easy to split, fragrant, easily forms coals, and doesn’t smoke much.

Native Americans may have helped spread the tree and might have traded in its fruits or cuttings in addition to its wood, Kimmerer says. But others think that the Native Americans who traded it, especially the Osage peoples for whom it’s named, would have had an incentive to trade the wood but not the fruits, since the tree’s restricted range gave them more or less exclusive access.

Regardless, European settlers took notice of the plant. Early French explorers called it bois d’arc—French for “bow-wood”—which eventually became bodark. In 1804, at the beginning of his famous journey with William Clark, Meriwether Lewis obtained cuttings of Osage orange in St. Louis and sent them to President Thomas Jefferson for propagation.

It soon became clear the tree also makes excellent fencerows. It sports sharp thorns on its lower limbs, and its wood is tenacious. When its branches are woven, or plashed, together, it develops into an impenetrable thicket.

The first “hedge mania” began around 1850. At that time, fencing was expensive and difficult to maintain. Feral hogs were an even worse plague then, compared to today. But Osage orange hedges—said to be “horse high, hog tight, and bull strong,” as the saying went—offered a solution. Jonathan Turner, a professor who promoted use of the plant in Illinois and beyond, was convinced that “God designed Osage Orange especially for the purpose of fencing the prairies.” He also helped established the University of Illinois, based in in Champaign—where I was raised and first met the fruits of Turner’s enthusiasm.

Learn morn about the importance of Osage orange as a hedge to the pioneers in this article by the Kansas Historical Society.

By 1869, around 60,000 miles of Osage orange hedges had been planted in the Midwest and South. Some consider Osage orange to be as important as the railroad, steel plow, and windmill for the settlement of the Midwest by Europeans, according to Michael Ferro, a researcher at Clemson University who wrote a scientific paper about the biology and history of the tree.

After barbed wire fencing became widely available in the 1880s, the use of Osage orange hedges declined, but the tree remained in use for its wood. Its popularity increased again following the Dust Bowl and Great Depression of the 1930s. President Franklin D. Roosevelt started an initiative, called the Great Plains Shelterbelt, to create windbreaks and protect farms in the Great Plains. Osage orange was the most popular tree used.

The tree was also popular for a time as an alternative host for silkworms. Throughout the 1800s, and into the early 1900s, silk farming had a series of booms and busts in the United States. Osage orange was sometimes used to rear the worms instead of mulberry foliage, though the trend didn’t last long.

Giants and ghosts 

The evolutionary prehistory of Osage oranges is a bit murkier.

Of the few animals that occasionally eat the fruit, none seem to disperse the seeds long distances. Evolutionary theory predicts that plants only make fruits this large for good reason. What reason could that be? Though the fruits do float well, they were found well outside of river valleys before humans came on the scene. So rivers can’t be the main way they spread.

Before and during the last Ice Age, all sorts of giant herbivores, most now extinct, lumbered and galloped throughout North America: mastodons, ground sloths, mammoths, camels, horses. Also glyptodonts, which ecologist Daniel Janzen compares to “a two-ton armadillo.”

Giant Ground Sloths roamed North America in the late Pleistocene era. They could weigh up to 2,200 pounds!

Janzen and other researchers think it was one of those giants that dispersed the Osage orange, with ground sloths or mastodons as the most likely candidates. And once they disappeared started around 13,000 years ago, the range of the tree remained a shadow of its former self.

This theory is hard to test, but there is some evidence to back it up. For one, researchers found what they believe to be Osage orange seeds in the fossilized dung of a mastodon, dating to about 12,000 years ago in what is now Florida. Another study found a DNA fragment in the dung of a Pleistocene ground sloth that could have come from an Osage orange.

The Osage orange, Maclura pomifera, has significantly larger fruits than its relative in the genus Maclura, which are found around the world. It began to diverge from Maclura brasiliensis, a tree now found in South America with a fruit less than half the size of a hedge apple, more than 20 million years ago, as shown in a 2017 study authored by botanist Elliot Gardner and colleagues. At this time, mastodons, ground sloths, and their relatives had showed up in North America and begun to diversify.

“It is reasonable to assume that a large fleshy fruit evolved to be dispersed by an animal, because large fruits are expensive for plants to produce … and today there do not seem to be any native animal dispersers of Osage orange,” says Gardner, who’s now at Florida International University’s Institute of Environment.

One problem with the theory, says Matthew Moran, a biologist at Hendrix College in Conway, Arkansas, is that hedge apples are unpalatable to most animals, full of a milky latex, with sensitive seeds. When he fed hedge apples to Asian elephants and horses, the seeds did not germinate after passing through the animals’ digestive system. Most fruits are put together the opposite way: The flesh is tasty, and the seeds are durable and often noxious—as is true for apples, for example.

With hedge apples, “it seems like things are very backward,” Moran says.

His hunch is that this “very strange plant … adapted to some individual species, that was very much a specialist, and that’s why we can’t find anything like it today.” A ground sloth is the prime suspect.

Kimmerer is skeptical. The tree, he says, “has done quite well without extinct animals … I’m not saying there was no role for megafauna in distribution of plants—what I’m saying is that it doesn’t help us understand anything, because it’s untestable.”

Paying attention

Lately I’ve become a bit obsessed with hedge apples—and talking to people about them. Responses are always interesting. When I tweeted about them last year, some people mentioned its use in repelling pests such as roaches or mice. But that’s a myth. Ferro spent many months tracking down the source of this tall tale, and eventually found it: A single October 1950 article in the Tuscaloosa News entitled “Roach-chasing orange found at university.” It wasn’t based on any solid evidence.

Others wrote to me to say that they ate hedge apples and found them to have general health benefits. “I puree them and bake the pulp until crispy, grind them up and mix into shortbread,” wrote a man named Brian Baxter. Extracts of the fruit have shown significant anti-cancer, anti-inflammatory, and anti-oxidative properties.

Connie Barlow, author of a 2000 book, Ghosts of Evolution, tried hedge apples as well. “The fruit tasted surprisingly good, but more like air freshener than food … delightfully clean, with perhaps a hint of cucumber,” she wrote. But the latex-y sap stained her hands and was difficult to clean off. A 1900 account that Michael Ferro turned up mentions that Queen Victoria took a small taste of a hedge apple brought to her by botanist William Hooker. It was apparently her only taste.

And that’s a strange thing about this tree: It’s not raised for food, nor is it an ornamental or an invasive. It doesn’t fit into the normal categories of most popular or widespread plants, Ferro says, and yet, “the history of the country would be very different if it weren’t for this tree.”

Osage orange’s history, and odd mix of superlative qualities, allow this strange fruit to continue fascinating people. Most of us know little about the plant world; we suffer from “plant blindness,” as some call it. The hedge apple rouses people from that indifference.

The other day I was walking down the streets of Georgetown carrying a hedge apple I had happened upon during a walk. A passing young man stopped me. “Can I ask: What is that?” he inquired. “Is it a seed? A fungus? I always wondered.”

“It’s a hedge apple,” I said, explaining—very briefly—the tree’s unfolding story.

We exchanged Instagram handles, and I promised to send him this piece. The hedge apple had found another receptive mind.

This article was written by Douglas Main and originally published in the National Geographic November 23, 2021 issue.