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.
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.