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.
Cosmos bipinnatus
Growth characteristics of this plant include:
Excessive rain can cause cultivation problems, due to the delicate nature of the stems. Heavy rain can cause breakage. "Cosmos bipinnatus" can tolerate heat as long as adequate moisture is provided, however, it does not handle droughts, strong winds or cold temperatures well. Snails, slugs and aphids have a taste for "Cosmos bipinnatus". Successfully cultivated plants can mature 2 to 4 feet x 12 to 18 inches.