Cleistocactus strausii
Silver Torch cactus can thrive in low-nitrogen soil without facing the consequences of low nitrogen. Too much water will make the plant weak and lead to root rot. 
Least Concern. This cactus is locally abundant in its native land and has few local threats to its survival.
This cactus can be propagated by cuttings or seed.
Disocactus × hybridus
Disocactus" × "hybridus is a hybrid between "Disocactus phyllanthoides" and "Disocactus speciosus". It is perhaps the most commonly grown orchid cactus and seems to survive and flower under most conditions. It has a very complex taxonomic history and has been mistaken for "Disocactus ackermannii" for a long time. The name "Cactus jenkinsonii" McIntosh (1829) might be an older name, but there is no combination under "Disocactus".