Christmas Cactus (Schlumbergera bridgesi) is a favorite holiday season house plant, but one which needs careful attention to details if it is to flower again the next year. It is closely related to Easter Cactus (Schlumbergera gaertneri) and Thanksgiving Cactus (Schlumbergera truncatus), all with fleshy, flattened, segmented joints and showy flowers ranging in color from white through pink, red and purple.
These cacti are epiphytes, which means that in their native habitat, they live in the crotches and bark of jungle trees. This is why they do best when grown in a light, porous, organic potting soil mixed with sand to provide excellent drainage.
When the flowering period is finished, an active growth period will begin. Keep the plant in a sheltered place until danger of freezing is over. Water carefully, keeping in mind that overwatering is the major cause of failure with Christmas cactus. Soak the potting medium when watering, and then allow the plant to become almost dry before watering again.
I have good success growing mine outdoors during the spring through fall in the bright, but indirect light found under tall trees, which is probably not too unlike the conditions where they are found in nature growing on the trunks of trees!
Fertilize with any water‑soluble, complete fertilizer with trace elements while it’s actively growing. Occasionally, leach out excess fertilizer salts with plain water.
Christmas Cactus will thrive in a well‑drained, sterile potting medium high in organic material. A little sand may be mixed with the medium to provide weight, important as the cactus increases in size. A pH of 5.5 to 6.2 is considered optimum for growth.
Although a temperature of 70 ‑ 80 degrees F during the growing season is considered ideal, plants will tolerate our outdoor East Texas temperatures in the 90 to 100 degrees F range, although growth may be slower. Slowly reduce water and fertilizer in August in preparation for the beginning of flower bud development, which is regulated by the shortening of fall days, along with cooler night temperatures. By late October and early November buds should be visible. Maintain bud set by adequate watering (not too wet or dry), taking care not to expose the plant to cold drafts, unvented heaters, or rough handling. Night temperatures above 70 degrees F may inhibit bud development.
I have had no trouble getting my Christmas Cactus to rebloom by keeping it outdoors until the night temperature gets into the 40’s. The cooler days and nights of fall, coupled with the longer nights combine to trigger flowering right on time, if not a little early for the holiday season.
As the plant becomes larger, short segments may be broken off and rooted in a loose, sandy medium very easily. Mealy bugs, scale and aphids may be rubbed away with a cotton swab dipped in alcohol. Use stronger controls such as houseplant insecticides only if the infestation appears to be gaining the upper hand. With good tending, Christmas Cactus should live for many years.