Christmas cacti (Schlumbergera truncata and its hybrids) and other similar cacti, often known as Zygocactus or Easter cactus, are found in the rain forests and cool mountains from Central America to southern Brazil. In nature, they grow in trees, rooting where organic material accumulates. This means that they are adapted to dappled, indirect sunlight, high humidity, abundant water, extremely rapid drainage and a very narrow range of temperatures, never too hot, never freezing.
Light: Treat your Christmas cactus much as you would any other house plant. It requires bright, indirect light. Dropping of buds or flowers is a frequent response to a dramatic change in light or heat. North or eastern facing rooms or porches are ideal.
Watering: Water when surface of the soil is dry. Take care that the plant does not dry out completely between waterings, just the soil surface. Water thoroughly, so that water runs out of the bottom of the pot. Continous watering systems should not be used for an extended period of time.
Growing Christmas Cactus Plants
Fertilization: Use a water soluble high-phosphorus fertilizer such as 15-30-15 at half the recommended formula for house plants. Fertilize once a month from March through August. Beginning a month before trying to initiate blooming, usually September for Christmas cactus and January for the others, cease to fertilize.
Blooming: The blooming of Christmas cacti is influenced by the increasingly long nights and cooling temperatures of autumn. As noted above cease to fertilize the plant in September. It takes 4-6 weeks for buds to form. To encourage bud formation, move the plant to an area where it will receive at least l4 hours of uninterrupted darkness (even street lights count) and the temperature will be between 55-65 at night. This can be a shed, a patio, a garage, a closet or any similar location. During this time, water half as often as you were previously, or just enough to prevent wilting. Temperatures above 75 degrees F will prevent bud formation.
Once buds have formed, control of the number of hours of daylight is no longer necessary and normal watering can be resumed. However, move the plant carefully and avoid moving to an area that is very bright, very warm or in a hot draft; the buds will fall. You should be rewarded with a profusion of flowers from as early as October to as late as January, depending on when the darkening period began.
Follow the same timing and procedure for the other varieties, but the entire cycle begins in January for bloom which will result from late March through April.
Repotting: Christmas cacti bloom better when somewhat pot-bound, but all eventually will need to be repotted. Use a well-drained, peaty soil mixture. The best time to repot is after blooming is complete. Test the drainage by running water through the pot to make sure it drains quickly. It is usually best to use a pot which is only one pot size larger than the previous pot, and lightly scratch or roughen the edge of the old soil to encourage root formation.
Pruning: These plants bloom on the new growth. To encourage more prolific blooming or to shape the plants, prune back to the desired size after blooming is complete. Simply pull or break off at the joints, no further treatment is necessary.
Problems: These plants are generally very easy to culture. They are occasionally afflicted with a bacteria infection which causes wilting from which the stem does not recover and a bark-like scale on the older stems. This condition is brought on by poor cultural conditions, usually a cycle of too dry then too wet, and is difficult to correct. It can result in the death of the plant, the best prevention is steady, regular watering and fertilization.
Propagation: These plants are typically complicated hybrids that must be propagated vegetatively. To propagate, break off a series of 3-5 joints and either place directly in water or in a light, moist sand. They will root readily. Be advised that most are named hybrids which are protected by plant patents and cannot be propagated for sale without permission.