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.
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.