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.
Harrisia fragrans
This is an erect or spreading cactus with narrow, long stems which can well exceed one meter in length, at times approaching five meters. It is covered in long, yellow or yellow-tipped spines which may be up to 4 centimeters long. It produces enormous tubular flowers up to 20 centimeters long which are sweet-scented and white to pinkish in color. They bloom at night. The fruit is spherical and red or orange in color, measuring up to 6 centimeters wide. The fruits are a favorite food of local birds, which likely help to disperse the seeds. The cactus has been noted to live at least 19 years, and in general has low fecundity; older, larger plants are more likely to survive, and they have higher fecundity, as well. Small plants may benefit from growing with nurse plants.