There was once a young man who went for a hike through the autumn countryside. When he felt like taking a rest, he sat down under a big oak tree and leaned his back against the trunk, looking out at the field of pumpkins that surrounded the tree.
"How very strange," he thought. "Those big pumpkins grow on skinny, weak vines that can't even stand up without climbing on something. Wouldn't it make more sense if pumpkins grew on something big and strong, like this oak tree?"
Just then, an acorn fell from the tree onto his head: blip! It bounced away.
"Whew! I'm lucky! If that had been a pumpkin, it would have smashed my head! I guess it's better that acorns grow on trees, and pumpkins lie on the ground."
This was a good year for acorns: many oak trees produced an abundant crop, and the squirrels were busy tucking them away for winter. Next spring, the acorns they didn't dig up will try to start an oak forest in our lawns and gardens!
Trees and animals often work together in spreading the trees' offspring to new areas. Sometimes, as with acorns and pecans, the new trees start from what squirrels overlook. Trees with tasty fruit, like persimmon and wild plum, have smaller hard-coated seeds that pass through an animal's digestive tract and get dropped somewhere new, along with some fertilizer. The animals help to spread the trees, and the new trees grow more food for the animals. It's a balanced partnership.
But what about Osage Orange (Maclura pomifera)? Why do those trees put so much energy into growing grapefruit-size green fruits, when it seems almost nobody eats them? In fact, their thorny trunks and branches hardly welcome an herbivore to get close. What's going on there?
One suggestion is that long, long ago, Osage Orange depended on giant ground sloths, mammoths, mastodons, and even ancestors of the horse to eat its fruits and disperse its seeds. In those days, Osage Orange grew over most of eastern North America! But when those animals went extinct thousands of years ago, the tree's range contracted to KS/OK/TX.
It was still useful, so people helped to grow it. Native American warriors prized its tough wood for making archery bows. French observers called it bois d'arc (wood for bows), hence "bodark" as one of its names. Before barbed wire was invented, pioneer farmers planted the spiny trees as windbreaks and hedges around their fields, and later used the strong rot-resistant wood for fence posts.
Sometimes horses take a bite of a "horse apple," and squirrels may chomp into the big fruits to dig out the small seeds. One of the "oranges" (they are really in the mulberry family!) can roll a good distance if it falls on a slope, but that's nothing compared to the travels of a mastodon. It's kind of sad to see the trees laden with big green "hedge apples," offering up their fruits to animals who disappeared millenia ago.
The hiker in my story was lucky that he didn't take a rest under an Osage Orange tree in autumn!
For an illustrated version of this story, see pages 14-15 of The Environmentor Vol 3 issue 3