Things You'll Need
Pot or planter
With their waxy flowers and segmented stems, Christmas cactuses (Schlumbergera x buckleyi) are usually grown as houseplants, but grow outdoors in U.S. Department of Agriculture plant hardiness zones 9 through 11. They grow best when slightly pot bound and seldom need to be repotted. They may require repotting if they fail to flower, dry out quickly or shrivel up soon after watering, which are all signs of exhausted soil. Repotting Christmas cactuses should be done in late winter after they finish blooming, and it should not be done too frequently or the plant may be traumatized and fail to bloom.
Combine 2 parts fresh, unused potting soil and 1 part medium-grit sand in a bucket. Stir the two components together until the sand is integrated and the whole mixture takes on a uniform appearance.
Soak the pot in a solution of 1 part bleach and 9 parts water for five minutes, then wash it in hot, soapy water to remove any debris. Rinse it well before use. Use a pot that is the same size as the Christmas cactus's original pot, or no more than 1 inch larger.
Place your hand across the top of the plant and flip the pot upside down to remove the Christmas cactus. Jiggle the pot until the root ball slides free. Place the plant, root ball down, on a flat work surface.
Crumble off roughly one-third of the soil from around the root ball. Massage the root ball to loosen the outer layer. Inspect the roots and cut off any with obvious defects such as mold or discolorations.
Make several shallow cuts through the root ball with a sharp, sanitized knife if the roots are heavily coiled, dense or impenetrable. Make the cuts horizontally at equal intervals around the whole root ball. Gently loosen the cut roots so they can spread out when putting on new growth.
Hold the Christmas cactus in the new pot with the base of the stems even with the top of the pot. Add the prepared soil mixture to the pot in small increments until the space between the bottom of the root ball and the bottom of the pot is filled.
Fill around the edges of the root ball with more soil until it is completely surrounded with soil. Shake the pot to settle the soil. Gently firm the soil around the root ball with your fingertips and add more soil, if necessary. Do not press the soil too firmly.
Put the plant back in its original spot, and facing the same way as it was before. Withhold water for one to two weeks after repotting so any broken or damaged roots have time to heal over. Resume normal watering after two weeks.
Always use pots with drainage holes, particularly when growing Christmas cactuses. Wipe the knife with a cloth soaked in rubbing alcohol or soak it in a solution of 1 part bleach to 9 parts water. This helps prevent the spread of disease.