Trichocereus Grandiflorus “Torch Cactus” is similar to many other cacti – it requires little water and likes partial to full sun. The latter means that it’s best to be kept outdoors.Besides, with some newer hybrids growing up to 1-2 feet tall and 12 inches wide, the Torch Cactus may be a too bulky cactus for indoor keeping.The Torch Cactus is more cold-resistant than the typical cactus – it can survive in temperatures as low as 15 degrees Fahrenheit (-9.4 degrees Celsius). While it still won’t survive harsh winters, it can do pretty well in mildly cold areas if kept dry.