Synanthrope (from the Greek syn-, “together with” + anthropos, “man”) is a member of a species of wild animals and plants of various kinds that live near, and may benefit from, an association with humans.

This time of year you simply have to be looking at the side of the road to find a weird, yellow-green, softball sized fruit lying in a road ditch. Look more closely and you’ll likely find several more. This is the fruit of the Osage-oranges (Maclura pomifera).

Osage-oranges are not a large tree in these parts, but they do have broad spreading crowns which create a dense canopy effect. They are perfect trees for climbing as their branches start low to the ground and are spread evenly throughout the trunk. Beware though, as the outer branches have thorns. The bark has an orange tint to it and is noticeably craggy and deeply grooved. The wood is dense and strong and makes great firewood and fence posts. The wood was a favorite of Native American tribes for bows. In fact, Osage refers to the Osage Native American tribe. The trees were used to create hedgerows as windbreaks next to agricultural fields. Hence of the tree’s common names, the “Hedge Apple”

What really makes the Osage-orange stand out is the aforementioned fruit. Contrary to its common name Osage-oranges are not in the orange family, but rather belong to the mulberry family. The large fruit is yellowy and pocked which gives it a slight brain-like appearance (if you use your imagination) and thus gives the tree one of its more colorful common names, “Monkey Brains”. These brainy fruits are technically edible, but they are very hard and thus unappetizing to both humans and other animals.

It is believed that Osage-oranges are ghosts from the Pleistocene. During the last Ice Age (over 10,000 years ago), North American was covered with large mammals (megafauna) such as the commonly known mammoth, but also mastodons, giant ground sloths and saber-toothed cats. The large herbivores (such as the ground sloth) would eat the Osage-orange fruit including the seeds. As the sloths moved along and pooped in new places they helped to spread the tree out. This strategy allowed for the Osage-oranges to make it all the way up to Ontario. Encasing your seeds in tasty fruit to be eaten and pooped by animals is a common way for plants to spread their seeds out. Once the megafauna became extinct, there was no easy way for the tree to disperse itself and now it’s natural range is slowly shrinking.

Osage-oranges are hardy, disease and pest resistant trees, so they can be commonly found in the overgrown wood lots that are tucked into cities. To find them just pay attention the next time you are biking, hiking or walking next to these pockets of woods – and look at the ground. You’ll likely see several, huddled together waiting for the giant sloth that won’t come.

Pick them up and check them out. They are fun natural toys to play with. They make great mini-boulders. Take them to the top of the stairs or a hillside and roll them down, watching them tumble and fall apart as they go. Or take them to a nearby stream and plop them in, they float well, and will bob along downstream. Even though you’re not a giant sloth, maybe you can act as one, as you disperse the seeds of the next generation.

To learn more about Osage-oranges check out the Nature Guys Podcast. Check out this article as well to learn more about Osage-oranges and other Pleistocene ghosts.