by Bruce Brethauer
Calibanus hookeri - is an unusual plant, with multiple tufts of evergreen, grass-like foliage growing from a cork covered, woody caudex which can grow to 3 feet in diameter (with at least one source suggesting that truly ancient plants may produce a largely subterranean caudex to nearly the size of a Volkswagen). The tough foliage may range from 12 to 36 inches in length and to barely 1/10 of an inch in width. The Caudex is covered by a thick corky bark which becomes deeply fissured as the plant grows, looking reminiscent of the so called tortoise shell plant, Dioscorea elephantipes. Even relatively young plants produce this characteristic fissured bark. The plants are dioecious, with male and female flowers being produced on separate plants. The inflorescence is a short panicle, growing to only about 4 to 8 inches in height, and is largely hidden within the taller growing foliage. The remains of several older flower panicles can be seen hiding amongst the dead foliage in this plant at the The Ohio State University Biological Sciences Greenhouse. The flowers are purplish and tiny; after pollination, the female plants produce red berries. After flowering, the leaves die from the tufts from which the flowers emerged - each tuft flowering only once. New tufts of foliage are produced from the apex of the caudex as the plant grows. Old plants produce many tufts of foliage, giving them a truly grass-like appearance when seen from a distance.
The following information is excerpted from the San Marcos Growers website
Calibanus hookeri was first discovered around 1845 but was not described until 1859 when it was misidentified as Dasylirion hartwegianum by Sir William Hooker at Kew. This mistake was quickly rectified by Charles Lemaire, who renamed it Dasylirion hookeri. In 1906 Joseph Rose established the then monotypic genus Calibanus to include this plant, but used the incorrect epithet "caespitosus" and William Trealease finally published the current name in 1911. Despite these early discoveries this plant went back into relative obscurity until it was rediscovered in 1968 in San Luis Potosi by Charlie Glass and Robert Foster and all plants now in cultivation were disseminated from this rediscovery. This rediscovery was recorded in the November-December 1970 Cactus and Succulent Society of America Journal (Vol. 42 No 6) in an article titled "Mexico Logbook, Part 5" by Charles Glass and Bob Foster where it was noted that the plant was found in 1968 at the top of a hill on mountain tops near Balneario de Lourdes in San Luis Potosi, Mexico. It turned out that this plant is fairly common on the hilltops of central Mexico, and has been used by the indigenous people, where it is known as Sacamecate, for thatching roofs as well as for scouring dishes, since it contains a soap-like compound in in the leaves. It is thought that because of its grass-like camouflage and mostly subterranean caudex, which has been described as up to the size of a Volkswagen, it was overlooked by most succulent collectors until Glass and Foster literally stumbled upon it after noticing children collecting its leaves - when they first tried to dig up individual clumps they kept breaking then off until they realized that they were actually standing on the large caudexes from which these tufts were growing. They brought back several large plants and collected seed which produced the plants sold at their Abbey Gardens nursery and later released through the International Succulent Introduction Program as Calibanus hookeri ISI 688. The genus is named for Caliban, the ugly monster in Shakespeare's Tempest and the specific epithet honors William Hooker. Besides the colloquial name Sacamecate, it is sometimes commonly called Mexican Boulder Plant. Calibanus was long considered the only species in a monotypic genus but a second species with longer and broader blue leaves and a much larger inflorescence bearing bigger flowers was discovered in 1995 in Guanajuato and was named Calibanus glassianus in 2003 to honor the late Charles Glass. Recent DNA work by DNA study by Vanessa Rojas-Piña, Mark E. Olson, Leonardo O. Alvarado-Cárdenas and Luis E. Eguiarte shows that Calibanus is nested squarely in the middle of the genus Beaucarnea, so this plant is now correctly Beaucarnea hookeri, but until such time that this name gets more recognition, we continue to list it as Calibanus.
This plant is easy to grow, and responds well to my basic guidelines for growing succulent plants. My plant responds especially well to life as a patio plant (once the risk of hard frosts has past). Full sun and warm temperatures are necessary for optimum growth - at least, here in Ohio where summer temperatures are not nearly as extreme as they are in the desert southwest; in those regions, this plant may benefit from some shade during periods of extreme heat. I give my plant an extra gritty potting medium to provide excellent drainage, Given a fast draining potting medium, Ohio's higher rainfall does not seem to bother this plant, but as it matures, it may be wise to lift the caudex slightly with each repotting, as a precaution against rot. Every year, my plant produces a good flush of leaves on each growing point, and typically adds a few new growing points as well, and the caudex shows a modest increase in size. I fertilize my plant several times during the growing season (spring through early fall) using a dilute solution of Miracle Gro Bloom Booster - but any number of fertilizers with a lower percentage of nitrogen will be fine for this plant. Inevitably, a certain percentage of the leaves becomes brown over the course of time - and will typically brown in response to a variety of environmental factors, including extreme drought, extreme heat, changes in light and temperature as a result of seasonal changes (a good number of the leaves on my plant will brown when I move my plant indoors in fall). Such browning is not a cause of concern, the dead leaves are typically retained on the plants for some time (possibly years) before being shed: in time, all plants will naturally retain a certain amount of thatch. Excess thatch can be removed for aesthetic reasons, but this is hardly necessary for the health of the plant. For those growers who insist on maintaining a lush looking plant with no browning leaves, this species will prove to be a high maintenance, as the multiple growing points will make it that much harder to trim away all of the older, dying foliage. For those growers who do not mind a bit of thatch on their plants, this will prove to be a very low demand plant, requiring only a minimum amount of regular attention.
To date, I have never seen any evidence of insect pests on my plant; the cork covered caudex appears to be impervious to insect attack, and the tough, fibrous leaves do not appear to appetizing to the usual problem insects of my patio - aphids and white flies do not touch it - and even Japanese beetles have ignored it. In spite of its affinity to the ponytail palms, which seem to be the favored greens of my cats, this plant appears to be of little interest to any of my cats. I suspect that the only vulnerable portion of this plant are its roots, so pay close attention to the roots when re-potting, and look for any indication of root mealy bugs. Growers in warmer regions may also be wise to check for evidence of spider mites. So far, spider mites have been of little concern for me - these pests proliferate under conditions of high heat, and low humidity, but to date, these have not been frequent pests in my collection.
I bring my plant indoors in fall when temperatures approach freezing, however, in regions with comparatively mild winters, this plant has proven to be adaptable; it will survive hard freezes down to about 10 degrees Fahrenheit, provided that it is given sharp drainage. I recall seeing a mature plant in a garden in the greater Raleigh area of North Carolina: provided the right micro habitat, this plant will survive in areas with moister, and possibly cooler conditions than originally imagined, and may be suitable for hardy cactus gardens, and xeroscapes into a zone 7, and may possibly be grown as an outdoor perennial far north as southern Virginia.
This is not a plant for every grower; while young plants can be maintained in relatively small pots for a good amount of time, plants will eventually achieve large proportions - the plant at the OSU greenhouse has a caudex which measures about 12 inches in diameter, and is maintained in a 14 to16 inch pot - I am guessing that it is 20 to 30 years old. The generally unkempt appearance of the grass-like foliage, and the tiny flowers will not create much interest in the plant. Even so, I would include this species in my list of essential caudiciform plants. The caudex of this plant is distinctive and full of character, and will eventually grow to a remarkable size. Unlike the majority of caudex plants which typically produce vines which may eventually ramble great distances, the foliage of this plant will remain comparatively compact: while the foliage may give the plant a disheveled appearance, it never looks out of control. Availability is another issue; plants can only be propagated from seed - both male and female plants are required for seed production, and fewer growers are propagating this plant. Back in the 1970s and 1980s this plant enjoyed a certain popularity in the wake of its "rediscovery"; but in recent years, interest has waned, and this plant is not so widely available. The Glasshouse Works frequently offers plants of this species, and is probably the source of my own plant (my plant was acquired from a former member of the Society), and may be available from other growers as well. Do not count on it being available at Cactus and Succulent Society shows and sales, since seed production requires two mature plants of proper gender, few collectors are actively propagating this plant. If you are a caudiciform enthusiast, and you encounter this plant for sale, by all means, give it a try.