Cleistocactus strausii
The cactus prefers free draining soils, strong sunlight, but not high temperatures — in fact it can withstand hard frosts down to -10 °C. In its natural habitat it receives plenty of water during the summer, but almost none over the winter. In cultivation, watering too much in winter often leads to root rot.
Houseplant care
Since almost all of the air circulation (transpiration) happens in the roots as does almost all of the energy production, the roots must be able to breathe easily. Overwatering will drown a typical houseplant. The air is pulled through the soil by the breathing of the roots. Air must be able to flow through the soil.