Keep an eye out for our Succulent City Youtube channel. Growing cactus requires patience. But it is also about being patient and keeping an eye out for potential problems. You will need to be more patient when planting your barrel-cactus outdoors. If the plant is still growing, it should be fertilized with a balanced fertilizer like a 20-20-20. If the plant is indoors, it is better to allow it to enjoy enough sun. After they have become used to living indoors, it is time to move them outside.