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Fruits of the osage orange

by William (Ned) Friedman, Director of the Arnold Arboretum
December 15, 2015

osage orage_Directors Blog 20

Fruits of the osage orange

osage orage_Directors Blog 20

This past week, it was hard to miss evidence of gravity at the Arnold Arboretum while standing by one of our osage orange trees (Maclura pomifera, 471-36*B). The delightful scene, looking a bit like a sea of abandoned tennis balls, can be found in the Centre Street Beds across from the Faulkner Hospital. Osage orange is dioecious so individual plants either produce pollen (male function) or fruits (female function). The very cerebral-looking “fruits” of osage orange are actually not single fruits, but rather are tightly packed multiple fruits that have developed from hundreds of individual flowers in tight clusters.

Of course, gravity is just part of the equation that leads fruits to fall from trees. Indeed, long before a fruit is destined to fall, in fact all the way back in time at a point when fruits are first being initiated from flowers, “abscission zones” with specific modifications of cell types and cell wall chemistry are laid down at a specific point in the axis of a fruit pedicel. While the gravitational pull between Earth and an osage orange multiple fruit remains constant, when the time comes to let go, a cocktail of enzymes helps weaken the abscission zone and the result is a lot of multiple fruits on the ground. 

Maclura pomifera is a member of the Moraceae or mulberry family. While this family of flowering plants is largely tropical and subtropical, we do have a few temperate members of this family, all of which have wonderful fruits to observe.  It is probably too late this year (I need to check), but next year, keep an eye out for the weirdly orange (multiple) fruits of Cudrania cuspidata (photo here).

-Ned Friedman, Director of the Arnold Arboretum

One thought on “Fruits of the osage orange

  1. To add a little twist to plant collecting, two, key Midwest horticulturists, John Pair and Al Ferguson spent time in the late 1970’s identifying thornless, male specimens for future propagation. Prime areas targeted for exploration included windbreak plantings throughout southern Iowa and eastern Kansas. There is likely tens of thousands of miles not yet explored. These guys recognized the extreme durability of M. pomifera to drought and resistance to disease and insects. Trying to get today’s nurseryman to grow them or a home owner to plant one is still a challenge. Granted it may not have outstanding ornamental characteristics and require some pruning to achieve acceptable form, it takes care of itself for many, many years! A colleague of mine once said, Osage are trees with higher education!

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