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 rigidissimus
"Echinocereus rigidissimus" natural habitat is distributed abundantly throughout Chihuahua and Sonora in Mexico, as well as in the United States in Arizona and New Mexico. It grows at elevation from 1200 to 2000 metres above sea level (Blum et al. 1998) 
This cactus prefers south facing slopes and is rarely seen on flat ground. It prefers the 1500 meter elevation. Plants are fire resistant from small grass fires but cannot tolerate hotter fires. With perfect habitat, these plants have been seen growing up to 45 centimeters in height. A 2018 measurement of one plant in the Santa Catalina mountains showed a height of 48 centimeters, a record. Flowering occurs from late April to early June depending on the elevation and spring heat. These plants will not flower when stressed but lack of flowering is rare. Their habitat has been negatively affected by cattle, cactus collectors and off road vehicles. These plants are becoming less common in southern Arizona.(S.A. Rasmussen 2018)