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How the pear got its spots

by William (Ned) Friedman, Director of the Arnold Arboretum
September 3, 2018

Pyrus bretschneideri

How the pear got its spots

Rarely, if ever, have I wandered through the pear (Pyrus) collection at the Arnold Arboretum and seen another person. So, this is a plea to venture to unfamiliar territory and enjoy looking at some wonderful pear fruits in various shades of green, with different fungal patinas—and take in their lenticel-spotted surfaces (more on lenticels below). Here you will discover that not all pears are pear-shaped!

Below are four of the Arnold’s fifteen species of pears (there are roughly 30 species worldwide in the genus): Pyrus ussuriensis (upper left, Ussurian pear, 188-98*A), Pyrus bretschneideri (upper right, Bretschneider pear, 437-64*A), Pyrus phaeocarpa (lower left, dusky pear, 165-2012*A), and Pyrus calleryana var. fauriei (lower right, Korean callery pear, 685-52*B).

Pyrus fruits

What are lenticels? Normally, these are small areas in the bark of a tree that allow for gas exchange for the inner tissues of the wood and bark. In pear fruits, the light brown and regularly distributed tan-colored spots are referred to as lenticels, but it isn’t clear that they actually are. Oddly, there has been very little study of these structures (I will have a look this fall under the microscope), but the assumption is that they help aerate the inner tissues of the fruit.

The pear collection at the Arnold Arboretum can be found just around the corner from the spectacular crabapple collection on Peters Hill, not far from Poplar Gate. In many ways, the pear collection is overwhelmed by the crabapples. But it need not be so; they are well worth a visit. And when you are done wandering the pears, go see the crabapples. They are as laden with a rainbow of fruits of all shapes and sizes as I have seen in many years.

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