Cleistocactus strausii
As a houseplant, the Silver Torch cactus is an easy to take care of so long as over-watering is avoided. To naturally simulate the porous effects of the sand in its native habitat, it's important to ensure that excess water will not pool in the soil, causing the roots to become water logged.
This plant’s native habitat does not have winter, but when temperatures drop to the low twenties, it can exhibit signs of tip frost. 
The Silver Torch cactus is most susceptible to 
mealybugs 
and spider mite.
Cactus
By studying the ratio of C to C incorporated into a plant—its isotopic signature—it is possible to deduce how much is taken up at night and how much in the daytime. Using this approach, most of the "Pereskia" species investigated exhibit some degree of CAM-cycling, suggesting this ability was present in the ancestor of all cacti. "Pereskia" leaves are claimed to only have the C mechanism with CAM restricted to stems. More recent studies show that "it is highly unlikely that significant carbon assimilation occurs in the stem"; "Pereskia" species are described as having "C with inducible CAM." Leafless cacti carry out all their photosynthesis in the stem, using full CAM. , it is not clear whether stem-based CAM evolved once only in the core cacti, or separately in the opuntias and cactoids; CAM is known to have evolved convergently many times.