Pamela Ruch is a horticulturist and garden writer. She holds a master’s degree in environmental science from Green Mountain College. Currently the director of the Urban Garden at the Nurture Nature Center in Easton, Pennsylvania, she teaches nature journaling workshops and hosts the website artofnaturejournaling.com.
 

 
 

Ghosts In Our Landscapes
by Pamela Ruch - posted 05/09/17

Osage orange: a fruit unloved by man and (existing) beast


Maybe you have seen the warty, lumpy, softball-sized green balls along the side of a country road. They fall from the trees in October and, more often than not, are still lying there in December. Maybe you’ve run over them, their soft yellowish flesh giving way with a gentle pop to the weight of your tires. Drivers behind you might notice the pulpy imprint of your passing. Like a pie crust under a rolling pin, the splat in the road flattens and expands with each succeeding set of tires; a day or two later it is likely to have faded to nothing.

The warty balls have a pleasant smell, a little like an orange peel. Unlike most tree fruits, they are not devoured by deer — or other animals either for that matter — but left to rot where they fall. The fruits are called “monkey balls,” “hedge apples” or, more commonly, Osage oranges, also the name of the tree that bears them (Maclura pomifera).

 

The seeds of the Osage orange are encased in soft, squishy flesh.

There is a theory about why the fruit of the Osage orange tree is so universally disdained (rumor has it that even spiders run from it although this has not stood up to the rigor of scientific investigation). According to science writer Connie Barlow, who is the author of The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronisms, (Basic Books, 2000), Maclura pomifera is an “ecological anachronism” with a ghost for a dispersal partner. The mastodons and wooly mammoths it evolved with had mouths big enough to take in the entire pulpy ball, and, the theory goes, deposit the seed in the course of their wanderings, enabling the tree species to expand its range to wherever the beasts might roam. As it is now, the tree is, literally, on a downhill slide. Seeds are dependent on gravity, or water, to take them to lower ground.

These Kentucky coffee tree pods (tasted and rejected by squirrels) are short and flat, rather than long and plump because there is not a male tree near enough for pollination to occur.

The Kentucky coffee tree (Gymnocladus dioicus) is another ecological anachronism. Though native, it is rare in the wild and found mostly on floodplains. Long after the branches are bare of leaves, female trees sport 5-10-inch, tough, woody pods, which fall to the ground in winter to be dispersed by water, if at all. Inside the pods are rounded, hard-shelled seeds encased in a sweet sticky pulp. So tough are the seeds that they resist germination, even after months of soaking — which makes you wonder how the tree was able to persist into the present. Barlow proposes that mastodons, which became extinct about 11,000 years ago, may have been attracted to the sweet pulp, and that they ground the pods between their molars, freeing the seeds and scarifying them so that they would take in water and sprout.


The pawpaw tree is native to the eastern United States. Unlike Osage orange, animals love the tasty fruits.
 

The theory of ghostly partners extends to other species as well. Pawpaw (Asimina triloba) is a temperate version of the banana or mango; except that those fruits can be picked when they’re hard and green, and, yes, shippable, whereas pawpaw has a shelf life of about a minute (OK, three days).

Clonal patches of pawpaw can be found in eastern forests, but they are apt to be distant from other patches, so there’s little transfer of pollen between genetically different individuals, therefore no helpful shuffling of genes. This is not a good survival strategy. In the case of the pawpaw, the suspected missing link is the pollinator. The flowers are not built for bees, and, according to Kentucky State University, “the natural pollinators of the pawpaw — various species of flies and beetles — are not efficient or dependable.” Barlow reasons that the pawpaw flowers were once pollinated by an insect, probably a beetle, that is now extinct. If the fruit were less perishable we would have more of an incentive to assume the role of pawpaw pollinator, which would help the species to survive — at least for the human-populated present.

The list of ecological anachronisms includes honey locust and gingko and desert gourds. The “ghosts” that left them behind were imposing creatures such as the mastodon and the giant sloth, as well as obscure insects, like the beetle suspected of servicing the pawpaw. And so, the story of fleshy fruits and woody pods that rot beneath the trees that bore them is the story of the earth. It is populated by the ghosts of dispersal partners and pollinators, a few of which leave behind clues that hint at their existence. Most, in all likelihood, do not.

 

This article appeared in a December 2014 edition of the State-by-State Gardening Newsletter.
Photography courtesy of Pamela Ruch.

 

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