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Cactus Spines Can Affect You Deeply

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The cactus and foot in question | Photo: Chris Clarke

A few days ago I kicked a cactus with my bare right foot. Three dozen spines lodged deeply in my skin: in the ball of my foot, the ends of my toes, in the folds between my toes. I managed to remove about two thirds of them. The rest were driven into my flesh with no protruding ends to pull or scrape away. There they remain.

I didn't mean to kick the cactus. I'm stupid, but not that stupid. We had a hard freeze a few days ago and a large cactus stem broke off from its mother plant. I let it stay where it had fallen, intending to let the break harden off for a few weeks so that I could plant it elsewhere in the yard without fungi invading the stem. It was well away from the sidewalk, I thought. It was too much trouble to put on shoes to take the used cat litter out to the trash, I thought. On my way back in I misjudged my step, and I literally saw stars for a moment.

The cactus in question -- pictured above -- was one of those cultivated Trichocereus hybrids you see in gardens all over California. Lucky for me. Its spines are only between a quarter- and a half-inch long, and relatively thin -- but not too thin. Aside from having to hobble around for a week or so and making sure none of the points of entry get infected, I don't need to worry much. If I'd kicked a cholla, I'd be in a lot worse shape.

It's a bad few months for my feet, desert wise. After more than two decades of wandering around in the desert, much of that time spent barefoot, and even more spent wearing hiking sandals, my feet had never found themselves the worse for a cactus encounter until the past six months. Last fall, heading out to check the mail, I trod unexpecting on a detached spine that had blown onto my driveway, tumbleweed style. That was more uneventful: the spine came out easily, and the pain subsided almost as quickly as the cursing.

This time did more damage. I've had to turn down two hikes so far, my right leg is developing a cramp from my late habit of walking on the inside of my foot, and I'm actually starting to consider that certain people around here might have a point about my putting on shoes before I go outside. Next thing you know I'll be cutting my hair and getting a job in marketing.

They're spines, by the way, and not "thorns," or "prickles." Thorns are modified branches, and prickles mere sharp hairs. Spines are highly modified leaves, growing from what were once leaf buds. In cacti, these modified leaves grow out of areoles, clusters of buds from which flowers and (in some cacti) leaves also grow.

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Areoles on a Mojave Desert beavertail cactus | Photo: Chris Clarke

It's the areoles that allow you to determine if a plant is a cactus. Lots of plants get called cacti that aren't, sometimes because the plant is a succulent but more often because it hurts when you bump up against it. Agaves and yuccas aren't cacti, nor are ocotillos, nor those picturesque and well-armed Euphorbias you see in office buildings.

Cactus spines serve an obvious defensive function, which becomes more important in the desert than in other parts of the world. Succulent plants are sources of water, which is in short supply in the desert pretty much by definition. A barrier of spines is often an effective deterrent to grazing animals that might otherwise rob you of your precious bodily fluids by chowing down on your leaves and stems.

It doesn't always work. Black tailed jackrabbits and Audubon's cottontails manage to eat prickly pear cacti despite the armaments, for instance. Many cacti have evolved subsidiary defense mechanisms, including bitter-tasting, emetic, and otherwise unpleasant chemicals in their flesh. Ironically, one species of mostly spineless cactus, Lophophora williamsi, has developed a chemical defense mechanism so effective that people have depleted it in quite a few parts of its range. It's far from the only cactus species that uses hallucinogens as a defense mechanism. Some are even common landscape plants in California, a piece of information which I note for academic purposes only.

Defense against herbivores isn't the only function spines perform. In many California desert species, spines also offer shade against the searing, implacable radiation coming from the desert sun. There are a few California desert cactus species, the above-pictured beavertail cactus among them, that rely on a thick waxy coating as protection rather than spines. But many desert species bear cloaks of spines so thick you can barely see the green skin beneath.

That's not a bad hint as to the origin of a cactus species, incidentally. Cacti don't just grow in deserts. The majority of cacti are native to habitats ranging from dryish, cold grasslands to tropical rainforests. Many of the most popular landscaping species originated either in the understory of montane conifer forests -- the common nopal prickly pear being an example -- or in deserts where coastal fogs provide some protection from the sun. The column cactus I kicked this week is probably an example there. In the Arizona Upland section of the Sonoran Desert, where rainy summer afternoons are far more common, many cacti show green through their spines, the saguaro being a fine example.

There's one other important function spines perform in some cactus species, primarily those belonging to the genus Cylindropuntia -- the chollas. If you're a large hairy animal brushing up against a patch of cholla, with or without shoes, it's very likely that some of that cholla will come along with you. Eventually you get it shaken loose and the section of cholla falls to the ground, where it can root out and start a new plant. In this way, the cholla's fiendish spines serve as reproductive organs of a sort.

Chollas and their cousins the prickly pears, by the way, have a type of spine unique in all of cactusdom: little hairy devils referred to as glochids. Glochids look benign when you encounter them for the first time, and more than one young child has learned to his or her sorrow that that fuzzy prickly pear cactus is not to be petted despite its velveteen appearance. Often growing in the hundreds per areole, glochids detach with almost no effort and easily burrow into your skin, where their barbed shafts and sheer numbers make complete removal almost impossible. (See this piece in KCET's SoCal Wanderer for tips on how to get most of them out.) As the pain glochids cause is slow to build, it's hard to resist the conclusion that their main function is punitive. Vindictive, even.

Back in the days when I worked in plant nurseries for a living, I had enough glochids work their way into my skin permanently that I'm probably about 2 percent cactus at this point. Thankfully, these aren't glochids in my feet. I work behind a computer now instead of moving large potted cacti back and forth, so I can manage to stay mostly off my feet for a day or five. Within a week the pain will ebb, and I'll begin the process of slowly absorbing those dozen spines into the tissue of my foot. You can make that 2.5 percent cactus, I guess.

Chris Clarke is an environmental writer of two decades standing. He writes from Joshua Tree regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here and follow him on Twitter.

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