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.
Echinocereus chisoensis
Because it is self-incompatible, flowers of one cactus require pollen from another individual of the species for fertilization; when plants are rare and spread apart, the likelihood that a pollinator will stop at the plant and deliver the correct pollen is lower. When fruits are successfully produced, they are often taken by jackrabbits and rodents for food. Dry conditions may increase this herbivory and decrease pollinator abundance.