QUESTION: My Christmas Cactus did not bloom this year. What happened?
ANSWER: There are several "holiday" cacti. They are Christmas Cactus (Schlumbergera bridgesii), with smooth 2 leaf margins or edges; Thanksgiving Cactus (S. truncata), which blooms earlier and has saw-tooth leaf margins and has oppositely pointed tips at the end of each leaf; and the Easter Cactus (S. gaertneri), which blooms naturally in the spring and has smooth leaf margins. These cacti species originated from the Brazilian jungle and grow naturally as epiphytes (in the air), in the branches and bark of trees.
These plants are short-day plants like poinsettias. Flowering is initiated by cool temperatures (45 to 55?), drier soil and the naturally shorter days of spring or fall. The Christmas Cactus in question did not bloom because one or more of these conditions were not met.
To induce flowering determine what type of cactus species you have. Ten weeks before blooms are desired place the plant in a cool closet or dark cupboard from sundown to sunup, never letting any light reach the plant during seclusion. Keep the soil drier than normal. Once flower buds are set you can cease this practice and increase watering.
Source: Houseplants. The American Horticultural Society, 1980. pp. 81-85