A Very Brief Overview of Cactus Spines

By Joe Bowman | joebowman.scienceblog.com

In the dry and parched lands of the Americas the cactus in all it’s many forms thrive in the some of the most challenging environments. 

In ecosystems where even the slightest advantage can mean the difference between survival and extinction each adaptation brings new opportunities for gaining advantages. The most recognizable adaptation of cacti is of course it’s penchant for a prickly persona. Cacti are best known for their spines – sharp protrusions typically  covering the entire plant.  Warding off hungry scavengers and punishing any inconsiderate or unwitting passerby foolish enough not to pay heed to these hardy plants.  While the adaptations of the cactus are many and worthy of exploration, today I bring you a very brief overview of cactus spines.

The spines of a cactus emerge from a unique feature called, areola. These highly specialized growth sites give rise to the spines of a cactus and allow plants some flexibility in arranging spine growth around the plant body.

Aerola are only found on cacti and are one the distinguishing features of this unique group of plants. Spines can have many different characteristics from large thick spines to many small spines to fine filamentous hairlike growth.  Some spine configurations are not entirely offensive in nature with some plants sporting pectinate spines that are soft and bristle-like and are held against the body.

Not to be ignored are glochids, very small, almost microscopic spines commonly produced by members of the genus Opuntia. Cacti armed with glochids are notorious for their unassuming appearance while closer inspection reveals their true nature.

This overview is far too brief to properly explore each type of cactus spine with any detail.  However, it is easy to recognize that the stately cactus is a surprisingly fascinating plant and the closer you look the more interesting they become.