Christmas Cactus (Schlumbergera bridgesii), Thanksgiving Cactus (Schlumbergera truncata), and Easter Cactus (Hatiora gaertneri, formerly known as Rhipsalidopsis gaertneri) do not have the typical requirements of most succulents. Although true cacti, they are epiphytic in nature, growing in the branches of trees in their native tropical forest rain habitats. The need for high humidity, bright but filtered light, and the soil kept relatively moist most of the year sets these plants apart from most cacti and succulents.
Holiday Cacti bloom at different times of the year, but all require short days and cool night temperatures to initiate flower buds. In fall, these plants should be kept in a bright location where the temperature drops to 55 to 65 °F (13 to 18 °C) at night, rising 5 to 10 degrees in the day. With 55 °F (13 °C) night temperatures, they will bloom in 5 to 6 weeks. If the night temperature is 60 to 65 °F (15 to 18 °C), these plants must have at least 12 hours of complete darkness every night for about six weeks to bloom. It is unlikely that they will bloom at higher night temperatures at all. Keeping the plants outdoors in a protected location until just before frost danger will result in abundant blooms, provided there's a cool, bright spot for them when brought indoors.
Holiday cacti should be potted in a standard cactus soil mix and watered thoroughly. Allow the soil to dry a bit between waterings. After they have finished blooming water less frequently, increasing again in spring or early summer when the plants resume more active growth. Fertilize several times with a dilute balanced house plant fertilizer during the bright light months, changing to low nitrogen, high phosphorus, and potassium formulation in the fall when flower buds are forming.
Once the buds have started to develop, holiday cacti do not like to be disturbed. Drafts or sudden changes in temperature or humidity-or even the direction of sunlight they receive-can result in dropping buds. If the plants are to be displayed in a warmer room than the one in which the buds were initiated, move them there as soon as the buds appear. As long as there is adequate light and a relatively cool night temperature, they should continue to develop normally and reward you with spectacular blossoms.
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