Consider the hedge apple. Why is it here? And what does it want?
When I was 4 years old my best friend was a hedge apple, and I mean that literally. My backyard in Ohio had a hedge apple tree, or Osage orange tree, and I was fascinated by the fruit it produced. Maybe I loved that the Osage orange tree, with its hedge apple fruit, could not make up its mind over whether it produced oranges or apples, and so went for a bright green, bulbous mixture of both. For whatever reason the sticky fruit was a delight to me. I would carry hedge apples around my yard, pull them in my wagon, and proudly show them to camera in one memorable childhood video.
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The best friend of my 4-year old self, enjoying a nice sunny afternoon. Photo credit: “Architect of the Capitol.” Click for link.
As I grew older, I forgot about my hedge apple friends until one day my professor brought them up in an invasive species lecture. Happily reunited, I began to wonder: what or who would eat a hedge apple? Why was it so much larger than most other North American fruit? And perhaps most importantly, had others made friends with the strange fruit? The answer involves mammoths, climate change, and a lost world resurrected.
The Osage orange tree in the backyard of my childhood home in Ohio. Photo Credit: Kathy and Doug Sales.
About 13,000 years ago, North America was coming out of the most recent ice age, and was full of woolly mammoths, giant sloths, and huge short-faced bears (this was a 5 ft. tall bear that could run over 40 mph. Not even Dwight Schrute could counter that one.). These giant animals affected the vegetation around them. The plants wanted the mammoths and giant sloths to eat their fruit because the fruit contains the seeds of the plants. By eating the fruit, animals moved the seeds far from the parent tree, and the plant species spread and survived.
The Osage orange tree once lived in a world where woolly mammoths, giant sloths, and short-faced bears were alive and moving around North America. Over time, the Osage orange tree grew large hedge apples, so that the giant herbivores of past North America would eat them. This tree also has large thorns on its trunk and near the top of the tree, to protect its bark and leaves from the ancient herbivores. The protection is another indicator that the Osage orange tree evolved in a world of colossal herbivores. Hedge apples, it seems, were a favorite of some ancient herbivore, because the Osage orange tree was once wildly successful. The huge herbivores of the last ice age moved the hedge apple trees as far north as Ontario, and 13,000 years ago, there were 7 species of hedge apple trees.
Animals of the last ice age, sans giant short-faced bears. Photo credit: Mauricio Antón, cc by 2.5. Click for link.
But as the woolly mammoths and other giant herbivores began to fade, so did the trees that depended on them. When early European settlers first arrived in North America, only one species of Osage orange survived. The hedge apple tree was only found in parts of Texas, Oklahoma, and Arkansas, a mere fraction of its once mighty domain.
So how did my 4 year old self find hedge apples in Ohio? It seems that early European settlers shared my peculiar interest in hedge apples, and would often carry hedge apples with them as they moved north and westward across the continental United States. The fruit and wood of the Osage orange tree actually contains an anti-fungicide, so perhaps they were useful to the European settlers, although they did not eat the hedge apples. Humans became the new giant herbivores, moving the Osage orange around like the ancient woolly mammoths. In doing so, Osage orange spread back across the continent, although the six extinct species are lost to us.
Today, Osage orange is considered invasive in some states, including Ohio, where I played with hedge apples as a child. This is because early European settlers only recorded it in parts of Texas, Oklahoma, and Arkansas. But sometimes it is important to remember the ancient world when determining invasive species. Osage orange, with its large hedge apple fruits, is actually dependent on huge herbivores and unlikely to spread and destroy other native plants. Plus, Osage orange had a much larger range in the not too distant past. The low invasive threat of Osage orange is especially true when remembering that these trees would have existed with many of our plants 13,000 years ago, which is a mere blink of an eye for a forest. The Osage orange is reclaiming its once mighty domain.
The hedge apple is a living ghost, a remnant of a world that once flourished right where we stand. With its brain-like texture and sticky substance, the hedge apple might look like it comes from an alien world, and in some ways, it is a relic of a world that no longer exists. Even though the last ice age is long gone, the Osage orange tree is still here, waiting for the return of the woolly mammoths and looking for human toddlers to befriend.
Rachel Sales is a Ph.D student, studying paleoecology. Find out more about her research here.