The barrel cactus genus Ferocactus (literally, “fierce cactus” in Latin) contains somewhere around 40 different species and a dozen or more varieties and subspecies in North America. Mexico has by far the most types, although the United States has either 5 or 6, depending upon which authority you accept. Within Mexico, the Baja California peninsula has somewhere around 12 to 14 species, making it a center of diversity for the genus. And of the Baja feros, one of the prettiest is the twist-spined barrel, Ferocactus acanthodes ssp tortulispinus. Read on for natural history information and habitat photos of this glorious plant.
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This F. tortulispinus is growing in front of a boojum tree (Fouquieria columnaris), one of the peninsula’s most signature plants. These fascinating and bizarrely beautiful relatives of the ocotillo (F. splendens) merit their own blog entry (and probably several of them) but we will focus on the twist-spined barrel for today. For a sense of scale, know that the cactus’ green body is about 6 inches (15 cm) in diameter, and the long, hooked central spines are about the same length.

A word on naming: The currently recognized full name of this barrel as stated above is Ferocactus acanthodes ssp tortulispinus, which places it as an outlier of the larger F. acanthodes complex which exists in the northwestern Mexican states of Baja California (norte) and Sonora, and in the US states of Arizona, California, Nevada, and a small bit of southwestern Utah. In recent decades F. acanthodes has also been called F. cylindraceus, but in 2014 or so it was changed back to F. acanthodes again based upon nomenclatural rules. If all this is confusing, then it’s primarily a self-inflicted human controversy, since the barrels themselves obviously don’t care either way what we name them.

While F. acanthodes has about 3 to 5 debated subspecies, mainly north of the border in US territory, F. a. tortulispinus is fairly well recognized for its distinctness and geographical separation from the rest of its clan, isolated as it is upon the Baja Peninsula. There is some discussion about whether it should be elevated from a subspecies to a full species ranking, however, based upon preliminary DNA analysis. Perhaps future genetic studies will support this conclusion. I will simply refer to the plant by the shorthand of F. tortulispinus for the remainder of this post, even though it’s not officially a full species yet.

As with many Ferocacti, juvenile plants are among the most attractive representatives of the species. The youthful, unblemished epidermis and comparatively long spines relative to the plants’ body size make for superbly appealing potted specimens in a collection. Older plants are still beautiful too, of course, especially when the spines are longer than average for the species. Most of these cacti have one lengthy central spine which is hooked and often twists, ranging from 4 to 8 inches long (10 to 20 cm).

Hooked spines are common in Ferocacti, since the strong spines can easily catch the sensitive noses of animals seeking to penetrate the plants’ defenses as they try to withdraw after trying to reach the water within the tissues. Anyone who has ever handled a hook-spined cactus knows how painful this can be on fingers, let alone noses, and that it’s easy to draw blood. Some of the spines are so hooked that they make essentially a full circle, like a shepherd’s crook. It’s unclear why this type of closed-looping might help the plant, since if the sharp tip is not available to grab onto the skin of critters seeking water because it’s become closed off, then it would seem to lose to protective function. Perhaps the isolation and relative lack of herbivores seeking to eat the cacti on the peninsula leads to this development which doesn’t happen in other populations of the F. acanthodes complex to the north? Perhaps there’s also a layer of chemical defense within the cells? Perhaps it simply doesn’t matter either way? Only research might be able to suggest what is actually happening.

This close-up detail photo of the spines of a F. tortulispinus demonstrate how the spines of Ferocacti actually grow. Note the regular pattern of raised ridging running parallel across the width of the spines. Each tiny corrugation indicates one day’s worth of cell division back when the spines were still soft and developing. Cactus spines can be thought of as being similar to fingernails, with a soft, pinkish-red living portion at the base and dead, lignified cells at the ends. While your nails grow continually from day to day, plant cells often only grow during the daytime when sunlight enables photosynthesis. This represents the raised ridge portion of a spine. At night, they pause and cells do not divide, making for the small troughs in between the ridges.

This pattern of ridging and troughing can be seen on many Ferocactus spines and that of certain other cacti as well, especially on long-spined varieties. There may be 150 or more tiny stop-start daily cycles represented on a long spine. But this does not mean necessarily that each spine is 150 days old before it stopped growing (which they eventually do) since Feros can grow rapidly in spring warmth, quit growth in summer heat, and resume it again in cooler autumn weather, pausing yet again during the coldest days and nights of midwinter. Dry periods might also interrupt spine growth at any time. Clearly then, when one counts the ridges, one can mainly determine that they went through 100 to 150 cycles of stopping and starting up again. But that doesn’t mean they did that all in one year, since the cactus’ ability to pause and resume weeks or months apart based upon temperatures or water availability could more than double that figure. A safe assumption however is to assume that each central spine took at least one year, and possibly up to two, to grow to full length before permanently quitting. Spines generally do not resume growth however, if the areoles they emerged from have moved down the stem from the active meristematic point of cell division as the apex; so at a certain point they are as long as they will ever be and will not grow again.

Some of the prominent compatriot succulents to the wild populations of Ferocactus tortulispinus include the noble, massive, green rosettes of coastal agave (Agave shawii), and the slender columns of boojum trees (Fouquieria columnaris.)

Also found mixed in with F. tortulispinus is the related Ferocactus gracilis. The two plants might be easily confused since both have bright red spines, but the F. gracilis tend to have shorter spines and not as much hooking at the ends. Additionally, flowers are yellow and bloom in April through June in F. tortulispinus, whereas F. gracilis flowers are red and flower in July-September. Based upon bloom times alone, this prevents the majority of potential hybridization, although it certainly seems possible that such crosses could occur occasionally. I do not know if this is actually true, but if it is, my guess is that the resulting individuals might appear somewhat intermediate, and actually would be pretty hard to definitively classify as hybrids based upon appearance alone. The thick-trunked succulent tree between the two F. gracilis below is an elephant tree, Pachycormus discolor, a member of the cashew family (Anacardiaceae).

I liked this photo of a seedling Ferocactus gracilis growing as an incidental epiphyte in the crook of a Pachycormus discolor trunk. In addition to just being a neat photo, it also shows the shorter and less-hooked spines of the species as compared to F. tortulispinus juveniles.

My friend Andy photographs a dead baby F. tortulispinus. It’s not uncommon to find these dried husks in a relatively intact form persisting for several years or a decade beyond the initial death of the young plants, since the long, interlocking spine clusters tend to be self-supporting even after the green flesh rots and flakes away once dried. Larger, older dead plants can also retain a semblance of this basketry, but they don’t generally remain cylindrical due to a larger span. Rather, these older collapsed barrels that are nothing but spines tend to look deflated, as it someone has let all of the air, or water, out of them. 😉

The habitat photos of the Baja twist-spined barrels above were taken in November 2014, while the next two photos were snapped in December 2017. I had sourced some potted 5 gallon plants of F. tortulispinus from a Phoenix grower and planted them in my gardens, and I was sorry to see one of the best ones had died one afternoon while watering.

This individual is like the ones above, about 6″ across with 6″ scarlet spines, whose brilliance was brought out even more by being wet. The plant has rotted and is mostly dead despite still being partially green. It will become one of those dry basket-like lattices within another few months. Normally I simply discard dead cacti without any fanfare, but in this case I decided to document the striking coloration, and make a post about the species at large. I may even just keep the dry husk hanging around for another few years in the garden for interest’s sake, even though I am bummed that the plant died. I do have several others, so hopefully those will continue to grow at least….

Lastly, did you know that the long hooks of Ferocactus tortulispinus spines make for dramatic and eye-catching jewelry? Andy demonstrates below.

No ear piercings are actually required, as the sharp hooks will catch onto just about anything they come near, and may even effectively do the piercing process for you if you are fortunate to move around just right. This desert chic look is becoming all the rage for botanists who care about wearing fancy attire while working in the field. From informal cookouts to weddings and debutante galas, Ferocactus jewelry is just the thing to make an aesthetic statement that will impress everyone lucky enough to witness it.

I think I know what to do with my dead barrel cactus now. See the merchandise section of this blog for availability. Earring pairs start at $2,499 each. Get yours today.