The Christmas cactus (Schlumbergera bridgesii) produces dainty pink blooms in winter near its namesake holiday. Usually grown as an indoor plant, Christmas cactus are only hardy outdoors in U.S. Department of Agriculture plant hardiness zones 9 through 11. You can separate the stems of an existing cactus and grow them into new plants by taking and planting cuttings at the beginning of the growing season.
Take cuttings from healthy stems in late spring or early summer. Select stems that are actively putting on new growth, because these are most likely to form roots quickly. Separate the tip of the stem from the plant, pinching or cutting it off at a segment joint. The cutting should have five three to five segments to ensure best growth. Dry the cutting in a shady spot for 24 to 48 hours so the cut end can scab over, which prevents rot and disease after planting.
A 4-inch diameter pot, filled with a sterile cactus potting mix or a combination of equal parts peat and perlite, allows you to root three cuttings at once. Water the mixture until it's barely moist and allow the excess water to drain out of the bottom of the pot for about 30 minutes before you plant. Insert the cuttings just deep enough so they stand up on their own. Covering the pot with a plastic bag retains moisture during rooting.
The cuttings will root most quickly if provided with bright but indirect light. The soil only requires watering if it begins to dry out. Water it only to lightly moisten the soil. It takes the cuttings three to eight weeks to form roots. Once roots form, the cuttings will begin to put on new growth and you will feel resistance if you tug on them lightly. Repot each cutting into its own 4- to 6-inch pot once the roots have grown to about 1 inch long.
The new Christmas cactus plants require bright light and temperatures between 70 and 80 degrees Fahrenheit to grow their best during summer, and temperatures near 68 F in fall and winter. Water the plants when the soil surface feels dry, but don't allow water to stand in the drip tray. Diluting 1/2 teaspoon of an all-purpose, water-soluble fertilizer, such as 24-8-16 blend, in 1 gallon of water and watering the cactus monthly during spring and summer after rooting, provides sufficient nutrients for healthy growth. Check the rates on the fertilizer label because they vary among brands.