Though I confess that plants held little sway among my childhood interests, a few specific trees stand out in my early recollections, all due to their memorable fruits. A seemingly ancient apple tree in a neighbor’s front yard was a climbing favorite, and bore small, mottled green fruits that were a delight to eat as long as you didn’t overindulge. Behind my grandparent’s garage in central Florida, a moss-covered orange tree provided fragrant spring flowers and slightly sour fruits that remain indelible sensations of my youth. But the fruits that perhaps fascinated me most belonged to an Osage orange tree that grew near my elementary school—large, hard as baseballs, and looking to us like green brains, the bumpy orbs with their citrusy aroma were a delightful mystery that inspired a number of ingenious games of our own design.

Large, round fruit of the Osage orange
The bumpy, softball-sized fruit of Osage orange (Maclura pomifera) matures in early autumn at the Arboretum. Nancy Rose

In earlier days, Osage orange (Maclura pomifera) garnered significant interest among people of its native Oklahoma, Arkansas, Missouri, and Texas, though for very different reasons. Hunters in the Osage tribe fashioned war clubs and bows from the tree’s bright yellow heartwood, which proved stronger than oak and as tough as hickory. Early settlers in the American frontier called it the hedge apple, planting it in thicket-like rows so that the thorny, interlacing branches sheltered fields from wind and provided an impenetrable animal barrier. As historian Paul Landacre famously described it, an Osage orange hedge was “horse-high, bull-strong, and pig-tight.”

For me though, even as an adult, it’s the fruits of these dioecious trees that really excite the imagination. If you cut one in half—and you may need a saw to do so—you’ll discover a tough, pithy core surrounded by a couple hundred small seeds. Like other members of the Moraceae (mulberry family), Maclura bears a true multiple fruit composed of numerous separate ovaries, each developing from a separate female flower. In fact, the fruit’s distinctive bumps—and their accompanying black, hairlike styles—rise from the fruit’s numerous, tightly-packed ovaries. Though squirrels rip into fallen fruits to consume the seeds, nothing else seems to find these forbidding fruits the least bit appetizing. Nothing, that is, that still exists. In her book The Ghosts of Evolution, author Connie Barlow suggests that mammoths, mastodons, and other large herbivores of the North American plains ate Maclura fruits and were its dispersal agents before humans evolved their own interests in the plant.

Although the exact details of the original collection of this monotypic species remain murky, we know that Maclura was among the botanical specimens gathered by Lewis and Clark on their transcontinental expedition of the American West. By studying saplings subsequently cultivated in the Philadelphia garden of Bernard McMahon, Constantine Samuel Rafinesque produced the first botanical description of the tree in 1817, naming it Ioxylon pomiferum, or “poison apple.” Perhaps unaware of Rafinesque’s classification, Thomas Nuttall offered his own description the following year, honoring American geologist William Maclure with its generic epithet and proposing aurantiaca (“orange colored”) as its specific epithet. Nearly a century later, Germany’s Camillo Karl Schneider argued for the name that has stuck to this day, pairing Nutall’s generic Maclura with a derivation of Rafinesque’s specific, pomifera.

Citation: Hetman, J. 2012. Maclura pomifera: Neither apple nor orange. Arnoldia, 70(2): 28–29.

Coincidently, this Teutonic connection to Maclura is compounded in the Arboretum’s most spectacular accession (471-36-B) of the plant, a female obtained in 1936 from the Hermann A. Hesse Nursery of Weener, Germany. Growing today on a steep bank near the Centre Street wall across from Faulkner Hospital, the tree exhibits the criss-crossing, nearly horizontal branching that once made the species so desirable as a hedging plant. It is 36 feet (11 meters) tall and its two trunks have diameters at breast height of 14 and 16 inches (36 and 40.5 centimeters). Visit it in autumn, when its limbs bend beneath the weight of its fruits and its glossy leaves turn yellow, and you’ll likely acquire fond associations of your own with this most singular of American fruiting trees.

Jon Hetman is the Arnold Arboretum’s Communications and Stewardship Officer.

From “free” to “friend”…

Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.

It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.

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