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.
Potting soil
Some plants require potting soil that is specific for their environment. For example, an African violet would grow better in potting soil containing extra peat moss, while a cactus requires sharp (i.e. plenty of) drainage, most commonly perlite or sand. But potting soil is not ideal for all contained gardening. Insectivorous plants, such as the Venus flytrap and the pitcher plant, prefer nutrient-poor soils common to bogs and fens, while water-based plants thrive in a heavier topsoil mix.