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.
Ferocactus wislizeni
The "fishhook" spines and the armored web of spines enclosing the cactus body are a defense against herbivory. Rarely a mature barrel cactus is found hollowed out by javelina but overall prickly pear experience much higher levels of damage from more species. Barrel cactus spines pose an extreme hazard for handling, penetrating boots and gloves. The roots are quite long but very shallow.