Although a cactus prefers slightly cramped growing conditions in a container, it may come when it outgrows its pot and needs a larger one. When the cactus roots reach the edge of the container, you must repot the cactus. With attention to detail and following recommendations, you can give your large cactus fresh soil in a larger container to continue to thrive.
Choose a container that is only 1 to 2 inches (2.5 to 5 cm) larger than the present container to ensure that you do not place the cactus in a pot that is too large. A cactus in a container too large may begin decaying because the soil will stay too wet. Fill the container approximately halfway with a cactus potting mix.
Wear leather gloves and long sleeves to protect your hands and arms from the cactus. Loosen the cactus from the container by inserting the trowel gently around the perimeter of the container. Wrap the cactus with newspaper so you can grasp it and work it loose from the container carefully.
Transfer the cactus from the old container to the new container. Set the cactus into the container so the plant will be at the same depth as it was growing in the old container. Fill additional soil around the cactus' roots and firm the soil down gently to finish repotting it.
Place the repotted cactus into its regular growing location with direct sunlight. Do not water the cactus for two to three days after repotting.
Tips and Warnings
Repot a cactus in the spring before the plant begins growing actively again.
Install a stake in the new container at the time you repot if your large cactus requires support. Choose a stake that is as tall as the cactus and place it into the container as you place the cactus into the container. Fill soil around both the cactus roots and the stake, then tie the stake to the cactus with stretchy plant ties.