by Bruce Brethauer
The Peanut Cactus is another one of those old timers which has been a popular houseplant for many decades - This is an attractive miniature plant with densely clustering stems, each measuring about 2/3 inch in diameter, and usually growing to a few inches in height, but occasionally growing to 6 inches or more. The stems are typically of an apple-green to greenish-yellow coloration, but in some clones the stems are of a bright yellow coloration - these clones typically lack a good percentage of their chlorophyll, and are therefore grown on grafts. When grown in very bright light, or otherwise stressed, some plants may produce reddish colored stems. The stems produce 7 to 10 shallow ribs bearing rows of short spine clusters. Areoles produce 10 to 15 whitish, bristle-like, spines which measure about 1/8 inch in length. The plants produce many offsets, and in time will produce an impressive cluster measuring from several inches to about a foot in or more in diameter. True to its common name, the individual stems are of a similar size to an unshelled peanut, and coupled with their shallow ribs, they do indeed resemble a peanut in general appearance. The stems are weakly attached; they are easily detached from the parent plant; these detached stems are easily rooted to establish new clusters.
A succession of flowers are produced in spring following a cool and dry winter dormancy. The flowers of this species are comparatively large - measuring about 1.5 to 2 inches long and across: in larger, established plants, the floral display can be so dense, that it will cover the plant entirely. In most clones, the flowers are a very bright orange-crimson, although other clones may produce yellow and white flowers. This plant has been extensively hybridized - primarily with various species of Lobivia (now subsumed within the genus Echinopsis): these hybrids exhibit a much wider range or flower colors, (primarily in reds, pinks and yellows), with somewhat larger flowers, and usually with somewhat more robust stems and spines than the species. Otherwise, these hybrids are quite similar in their general appearance, and their cultural requirements to the species.
The Peanut Cactus is native to Tucumán Argentina, and occurs at elevations to over 4000 feet. It exhibits a good degree of frost hardiness - online references suggest that this plant will survive temperatures down to 20 degrees Fahrenheit provided that the plant is kept dry. It is regularly grown outdoors in southern and costal California, as well as Florida, south Texas, and warm winter regions of Arizona. It has also been grown outdoors successfully in England and in the warmer winter regions of the Pacific Northwest. In cultivation, it probably requires a cool winter dormancy to insure a good flower set in the spring, and may benefit from especially cool conditions (frequently down to 45 degrees) at this time. In decades past, when many households did not have thermostatically controlled furnaces, and night time temperatures frequently dropped to very low levels on cold nights - this plant probably proved to be hardier than other cacti which originated from somewhat warmer regions - making the Peanut Cactus an especially popular plant with growers in cold winter areas in decades past.
The proper name of the Peanut Cactus has changed several times over the years: many old timers will know it by the name Chamaecereus silverstrii, but it has also been called Lobivia silverstrii, and in most recent treatments, it is called Echinopsis chamaecereus. Earlier references suggested that this species was not known to self in cultivation, leading to speculation that the plants in cultivation may have been sterile hybrids. In subsequent books, it has been suggested that only a very few closely related clones found their way into cultivation initially- and these were so closely related that they were self incompatible - incapable of producing viable seed. In recent years, additional clones of this species have found their way into cultivation - and it appears that at least some of these have been able to produce viable seed when crossed. Even so, it appears that the preferred method to propagate additional plants is to root the numerous offsets and branches produced by this plant.
This species responds very well to the general guidelines for growing cacti and other succulents, but may benefit from especially cool conditions during its winter dormancy - possibly down to temperatures as low as the upper 30's and lower 40's for example. During the winter, these plants may be maintained in such cool places as the windowsills of attics and attached garages, breezeways, three season rooms, enclosed porches, "mud rooms" and other areas which can get quite chilly, but not quite freezing cold. My plant is still quite small, and is now being over-wintered on the windowsill in the airspace between the outside window and a weatherproofing sheet of plastic, a position which it shares with other very cold tolerant succulents. The Peanut Cactus also has the reputation of being a bit more tolerant of shade than many other succulent species: in regions with very hot summer temperatures (Southern California, South Texas, and Phoenix and Tucson Arizona for example), this species will require some shading to prosper - otherwise plants will tend to scorch. In northern regions with somewhat cooler summers and reduced solar radiation - this plant will still benefit from full sun, and does not appear to require any shading - even when moved outdoors during the warmer months. This plant also has the reputation of being a fast grower, and will probably benefit from somewhat more frequent applications of fertilizer during its growing season.
Despite its popularity in years past, the Peanut Cactus seems to have fallen out of vogue in recent years, and is proving to be a bit more challenging to locate in the trade today. Occasionally this species, or one of its hybrids may be found in a mixed succulent dish garden, but it is practically impossible to locate individual plants, or specific varieties and hybrids at any of our local nurseries. It can be found online, and through mail order nurseries such as Grigsby Cactus Gardens, Bob Smoley's Gardenworld and Mesa Garden, and can probably be found in the collections of some of the members of the CSSA, so one good way to find plants may be at one of the sales of the affiliate clubs of the Cactus and Succulent Society of America.
It would be hard to find a cactus which was better suited for the average household than the Peanut Cactus. It tolerates a wide range of growing conditions, and seems to tolerate light shade better than some other cactus species, making it a better choice as a houseplant than some cacti which may require more intense light than is available in the average home. This is an easy plant to grow, presenting few problems or challenges, and is frequently recommended as a terrific starter plant for hobbyists and younger growers. Its short, bristly spines are unlikely to cause injury, making this plant especially suited to households with children and inquisitive pets. It also has the reputation of being a relatively fast grower, and will eventually fill a pot with its numerous offsets. Even so, this is a compact plant, and can be maintained in small pots to fit on windowsills and other small spaces. And best of all, it has the reputation of being an easy bloomer - with many clones reliably producing a stunning annual display in spring following a period of winter dormancy. It is really difficult to find any problems with this species - other than its branches are weakly attached and that detached stems will occasionally fall from the plant and onto the windowsill or floor - but even this is not much of a deterrent- as these stems can be rooted to establish a new plant which can be given away or traded with other growers. If you know of someone who is new to growing cacti, and wants something easy and reliable, this is an excellent plant to grow. For those of us who have been growing cacti and other succulents for many years - it may be time to give this little gem a second look.