Most prickly pear cacti grow out of the ground, but one intrepid member of the species has taken root in a more exotic locale: the trunk of a tall saguaro in Sabino Canyon.
The somewhat quirky cactus collaboration is playing out in the Desert Garden, a site along the canyon’s Bajada Loop Nature Trail.
Botanists and some casual observers have come across other examples of prickly pears hitching a ride on saguaros or other large cacti — but it’s fairly unusual, said Mark Dimmitt, a cactus expert and retired director of natural history at the Arizona-Sonora Desert Museum.
“I don’t know that anyone has dissected an example to determine whether these plants are growing epiphytically or have actually grafted onto the saguaros, effectively becoming parasites,” Dimmitt said. An epiphyte is a plant that grows on another plant but isn’t a parasite — instead deriving its moisture and food from air, rain and accumulated debris.
“All of the aerial plants I’ve encountered appeared to be barely surviving, becoming severely shriveled during the dry season, so I’m fairly confident that they are not tapped into their host’s tissues,” Dimmitt said. “It’s more common to see cacti and other plants growing on the trunks of palm trees. They have rough fibrous surfaces that can absorb and hold water for some time after rains.”
