To flower, your Indian head cactus needs a cool winter dormancy period. In its natural habitat, it experiences a drop in temperature and shorter days during the winter months. You can simulate this by keeping your cactus in a cool room (around 50-60 degrees Fahrenheit) with little to no light for about six weeks. After this period, slowly transition the plant back to its regular growing environment. Then, with proper care, your cactus should bloom in late spring or early summer.