It’s hard to kill a prickly pear

This is a prickly pear cactus that turns purple during the winter months.

By Rick LoBello, Board Member

Some of the plants that we have living here in the Chihuahuan Desert are much more resilient than most of us realize. When you think about the extreme periods of drought and temperatures that they have to endure, we should not be surprised. Take for example the prickly pear cactus.

Prickly pears are some of the most common cacti we have living in El Paso in both our backyards and all over the desert mountain region that surrounds us. I have always known that this cactus was about as hardy as they come. Did you know that if you cut one into pieces and just scatter the cut up pads, chances are very good that new plants will sprout up when roots start growing out from the tiny clusters of spines called areoles?

This is a sea urchin. From a distance some prickly pear buds look like sea urchins.

Back in 2021 during a very dry period, I went for a hike at the Westside Regional Park and took a picture of a dead prickly pear that was covered with clusters of spines resembling sea urchins. According to my good friend Dr. Ad Konings, who is co-author of Cacti of Texas in their Natural Habitat (2009), he thinks that these are prickly pear “buds” also called areoles that start to grow and perhaps try to make a new pad. When there is not enough water to grow a new pad, we see a bunch of spines. These spines are called glochids. If you have ever collected prickly pear cactus fruits you probably have experienced these tiny and very irritating spines getting into your skin. These tiny thorns are actually needle like leaves that shade the flesh of the cactus to help it retain water. Dr. Konings reminded me that “it is just hard to kill a prickly pear!”

Prickly pear buds growing from the dead stems of a prickly pear cactus.

The prickly pears near my house had all turned purple. According to Dr. Konings not all prickly pears turn purple under stress, but the purple ones near my house (Opuntia macrocentra) were good examples. The purple pigment is betacyanin. Dr. Konings says that he can “think of two different processes that could cause the plant to turn purple under stress:

1. When there is ample water the plant can photosynthesize and the amount of chlorophyll that covers the outside of the stem probably obscures the stem’s purple color. Perhaps with decreasing photosynthesis also the amount of chlorophyll decreases and there will be less green on the plant and the purplish pigment becomes more visible.

2. The betacyanins are susceptible to heat as they break down at higher temperatures. So when day time temperatures don’t get to a certain threshold the betacyanins stay intact longer. With the decrease in photosynthesis perhaps the pH of the cell plasma changes where the pigment becomes more intense.”

Now you know more about the prickly pears in El Paso than most people. Enjoy the outdoors.