By Cynthia W. Mueller
Master Gardener, Galveston County
Christmas Cactus (Schlumbergera bridgesi) is a favorite holiday season house plant, but one which needs careful attention to details if it is to live and 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 are cacti which in nature live in the crotches of jungle trees, and benefit from light, porous soil mixed with leafmold and sand.
When the flowering period is finished, an active growth period will commence. 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, then allow the plant to become almost dry before watering again. (When the plant is put outside during warmer weather, it will be easier to keep if placed on the porch, or in a situation where it will not be soaked with rainwater over a period of several days). Fertilize with a water-soluble 20-20-20 fertilizer with trace elements while in an active growth stage. 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 Texas-type temperatures in the 90 to 100 degrees F range, although growth may be slower. Reduce water and fertilizer in August in preparation for the beginning of 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 in evidence. Help to maintain bud set by adequate watering, 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.
As the cactus becomes larger, shorter tip portions may be broken off and rooted in loose, sandy medium with very little trouble. 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 may live for many years.