Holiday cacti take their place with kalanchoes as popular gift plants, but their care is quite different. They can bloom season after season with the right amount of water and sunlight.
Thanksgiving cacti and Christmas cacti are both varieties of Schlumbergera, also known as Zygocactus. Each variety is known for the time of year it blooms in the Northern Hemisphere. S. truncata have leaves with pointed teeth and bloom in the fall. Schlembergera in the Buckleyi group have leaves with rounded teeth and bloom closer to winter. Easter cactus, Hatiora gaertneri, is a similar epiphytic cacti, but a different genus. Holiday cacti are available in red, deep pink and white.
Schlumbergera is photoperiodic, which means its bloom time is related to the number of hours of darkness it receives each day. If you want your Christmas cactus to bloom in December it needs 13 hours of darkness each night beginning in October and continuing for six to seven weeks. Many people put their Christmas cactus in a closet for the night if they live where there is bright outdoor lighting.
Holiday cacti are native to coastal Brazil and grow in a moister environment than desert cacti. When they are raised in a green house the humidity is kept quite high. If you bring your plant home to a warm house in the winter it may drop some blooms because of the change in humidity. You can overcome this by keeping your holiday cactus near a source of water as you would do with an orchid. Be sure the roots are not in water.
Unlike other cacti that should dry out between watering, holiday cacti should be kept moist. Only the top of the soil should be dry. Watering is beset done by submerging the bottom of the pot in a tray of water and allowing the water to be absorbed up through the holes in the bottom of the pot. When the plant begins blooming watering can be reduced. A balanced fertilizer (one with the same three numbers) can be applied during the growing season and discontinued in October when the plant will start to set buds.
Schlumbergera also do better when crowded a little, so keep your cacti in a small pot. When it grows too large for the pot, move up one only slightly larger. Repotting should be done after the plant has finished blooming.
About a month after blooming the plant can be pruned if it looks too lanky. Pieces that are two to three sections long can be used to start new plants. After the cut end has dried, place it in cactus mix and lightly mist it. It will take a several weeks to root.
Holiday cacti are bothered by few pests. Aphids can be controlled by a spray of water and mealybugs can be dispatched with rubbing alcohol applied with a cotton swab. Mealybugs are more likely to be a problem if the soil is kept too moist.