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.
Echinopsis eyriesii
Water the plants well in summer, but let them dry before watering again. Use then special fertilizer for cacti.
In winter keep dry. The temperature may be as low as -7 °C. For flowering in summer, the rest (dry and cold) in winter is necessary.