Cacti, the Fog and the Desert—Copiapoa
Our Bay Area winters, chilly and humid, are the antithesis of what most cacti need to thrive. Right now, while those plants that live in the southern hemisphere bask in the summer sun, those from Mexico and the Southwest endure their winter rest, with no rain and almost no atmospheric humidity. A certain number of cacti and other succulents, however, have managed to adapt to one of the planet’s truly rare and bizarre environments, those coastal deserts where the combination of hot sun and cold ocean current produces a steady plume of fog blowing across the parched landscape. These fog deserts—and there are only a few of them in the world—each comes with a complement of peculiar, highly adapted succulent plants. Perhaps the most famous fog-desert lies along the coast of north-west South Africa and Namibia . A second, much closer to home, covers the central, seemingly desolate but succulent rich, section of Baja California . The third, in northern coastal Chile , is home to our succulent of the month, the highly specialized cactus genus called Copiapoa.
When the wind dies down in one of these strange places, the temperature rises rapidly, but much of the time the climate is surprisingly mild, with an often daily light soaking of air-borne moisture. Without including the fog, the precipitation totals for these areas is astoundingly low; perhaps a few inches of rain a year along the Namibian coast, an inch or two in central Baja, and for much of coastal northern Chile , literally no rain at all, sometimes for decades at a time. The resultant landscape must be one of the very bleakest on Earth, almost completely devoid of vegetation, of any life, except within a clearly defined, narrow band alternately obscured and revealed by fog. This is the landscape that has molded copiapoas. Copiapoas grow along the edges of the fog zone; above or below the fog’s cat’s feet even they can’t live, while in the middle of the zone the excess moisture will rot them out. A few other plants share their environment, particularly those places where a little actual rain occasionally falls; some other cacti, some terrestrial bromeliads. In the driest regions, though, there’s nothing much except colonies of copiapoas and the skeletons of other cacti that have failed to survive the area’s increasing aridity . Copiapoa is not a large genus, with slightly more than two dozen reasonably valid species. As is often the case with cacti that have erratic distribution patterns, each population differs from the next, giving rise to a large number of apparently separate “species” that are really no more than minor variations. Regardless of the taxonomy, though, copiapoas display a wide variety of forms. Some, such as C. tenuissima and C. laui, have reduced spines, tiny dark bodies and in their habitat are mostly underground or concealed in crevices in rocks, with their tips barely poking above the soil line. Others, among them C. humilis and C. hypogaea, form clusters of small, brownish-purple cylinders with black spines. Copiapoa krainziana has long, white bristles for spines, especially when “young” (say less than fifty years old). The most distinctive species, such as C. cinerea and C. haseltonii, grow very slowly into slim, medium sized barrel-cactus-like shapes, made striking by a waxy, stark white, slightly golden, or pale, ashy-gray epidermis set off by relatively sparse yellow, gray, or jet-black spines. These larger copiapoas may remain solitary or may slowly clump either from the base or from higher on the main stem. In habitat they often point north, maximizing the amount of light they receive. Many of the large copiapoas develop a dense covering of white or golden wool at their apices, where they display their pale yellow flowers. In their habitat, large clusters of copiapoa, often spaced at regular intervals from each other, in places where even other genera of cacti can barely hang onto life, seem almost like alien life-forms. In the wild their growth rate is very slow, but in the more hospitable circumstances of cultivation they will speed up a bit. In cultivation their needs are a bit different from most cacti. Some of them have tuberous roots, and all of them are susceptible to rotting if given too much water. Few copiapoas can withstand much cold, as none of them live at very high altitudes. They need very bright light, but are somewhat susceptible to sunburn. Because their habitat varies relatively little from season to season, they don’t require the absolute winter drought of some other cacti. I water mine about once a month or month and a half in winter, but during the warmer months I keep them somewhat drier than many cacti, watering them perhaps every ten days or two weeks. Though they look strikingly different from typical cacti, as long as they are kept from cold and not given too much water or a soil with too much organic matter, they aren’t all that difficult to grow. The smaller plants grow more quickly and are somewhat easier, but the larger species with their strange, alien-looking colors and forms, though hard to come by are the most desirable.
The Garden has a good collection of copiapoas, including many old plants. We sometimes have seedlings available for sale.
