Last week I had a long, wet bike ride in to UBC Botanical Garden, and was contemplating which species I should write about. The miserable weather made me long for the dry summers of my youth, spent in the Okanagan Valley, and I resolved to write about a cactus that I am much too familiar with, Opuntia fragilis. Thankfully, I was able to find this gorgeous photo of a brittle prickly pear cactus in bloom.
It is not often that I complain about being too familiar with a plant species, but in the case of the brittle prickly pear, this is true. I have experienced this diminutive cactus with most of my senses: the slightly spicy scent of the flowers, the taste of the sticky pads (somewhat edible) and the sight of the delicate, diurnal blooms (I’ve always appreciated these). However, my sense of touch did not appreciate the plants I didn’t see in time. My hands, my feet, and in particular my shins, have been subject far too often to the barbed spines of this cactus. My experience with this species is nevertheless much less intimate than that of my son’s, who had the misfortune of sitting on a large mat of brittle prickly pear at the tender age of two.
Although close contact with Opuntia fragilis spines is not recommended, they are quite fascinating to contemplate from the safe distance of the Botanical Garden office. The spines of brittle prickly pear emerge from areoles that are distributed in diagonal rows across the surface of the pads. From the areoles emerge spines as well as glochids, which are fine bristles, 1-2mm long, and have a brownish-red colour. The spines are light grey, are found in groups of 2-6 per areole, measure 5-30mm long, and have a nasty barb at the tip. The combination of the two types of spines helps make Opuntia fragilis so painful.
The experience of being impaled by a brittle prickly pear goes something like this: first, one must rip away the pad, along with the spikes. In my opinion, this is best done as one would rip off a band-aid – quickly and without too much contemplation. Depending on how many spines have gripped into one’s flesh, and how deeply they are embedded, this can be mildly painful to excruciating, and some blood may result. The uninitiated will, at this point, believe that they are quite finished with the experience, but eventually they will notice that the pain inflicted by the Opuntia fragilis is only getting worse. Upon closer examination, the victim will notice that many tiny, hair-like spines are still aggravating their flesh, and will have to sit down with a good pair of tweezers to painstakingly remove each glochid from their skin (which is what veteran brittle prickly pear victims know to do right away).
The spines serve Opuntia fragilis in at least two ways. Firstly, they offer effective protection against fauna looking for a taste of the watery flesh–a precious resource in the dry climates where this species is found. Secondly, they provide the primary means of dispersal for this species. The cladodes (pads) easily break off from the rest of the plant when a person, animal, or vehicle gets hooked by one (or more) of the cactus’ spines (the terms fragilis and brittle refer to this quality). The cladode is carried until its vector realizes that it has been stabbed, at which point it is ripped out and tossed aside. If the pad lands on soil, it will live off of its fleshy reserves until it has established a shallow, fibrous root system, and will begin to form a new mat of cactus pads. This reproductive strategy seems to be working quite well–Opuntia fragilis populations are found widely throughout western USA and Canada, reaching as far north as 58°N in Alberta and British Columbia (the northernmost species of Cactaceae in the world). The range extends as far south as Texas and as far east as Ontario and Michigan.