Meet your Houseplant: The Bunny Ears Cactus
Bunny ears are soft and pleasant to pet. The same cannot be said of the bunny ears cactus. The bunny ears cactus (Opuntia microdasys) is a small ornamental species of prickly pear native to Northern Mexico. It grows in short, dense shrubs of pad-like stems and has become popular among cacti enthusiasts because of the young plant’s resemblance to a bunny head. Its species name, “microdasys,” means “small and hairy.” At first glance, the cactus is indeed hairy, but be careful; that’s not bunny fur.
O. microdasys is covered in glochids, tiny clusters of hair-like spines. One glochidium can easily contain a hundred spines that range in length from 0.8 - 2.5 mm and are only 0.03 to 0.07 mm wide, thinner than some human hairs. Unlike other cacti with large, intimidating needles, cacti of the sub-family Opuntioideae are covered in barbs that spiral downward from the spear-shaped head of the spine to its base. The spines are easily detached by a slight touch or even a gentle breeze. If they become embedded in tissue, they are not easily removed and can cause serious irritation.
The glochids of O. microdasys undoubtedly serve a defensive function against hungry herbivores, but there is more to these spines than their obvious painful, pointy-ness. Glochids are specialized for collecting fog. In the desert, where water is scarce, nighttime fog collects as droplets on the spines and are then funneled down to the spine’s base, where the water is quickly absorbed by small, tender hairs called “trichomes.” The properties of the spines are such that their water collecting can defy gravity. Even when a spine is held at 90 degrees with its point toward the ground, water droplets placed at the spine’s tip still wander upward to the base and are greedily absorbed.
O. microdasys is definitely a look-but-don’t-touch kind of plant. And if you begrudge it for pricking you, just remember it’s not personal. It’s spines didn’t evolve necessarily to cause you pain. It was just thirsty.
Brian Rutter, PhD, is the cofounder of Thing in a Pot Productions and a postdoctoral researcher in plant biology at Indiana University. Subscribe to our newsletter to receive our “Things About Things – Odd Facts About Plants” and video production tips in your inbox every month!
Works Cited
Ju, Jie, et al. "A multi-structural and multi-functional integrated fog collection system in cactus." Nature communications 3.1 (2012): 1-6.
Whiting, D. A., and J. H. Bristow. "Dermatitis and keratoconjunctivitis caused by a prickly pear (Opuntia microdasys)." South African medical journal= Suid-Afrikaanse tydskrif vir geneeskunde49.35 (1975): 1445-1448.