Right now, I have a Thanksgiving cactus blooming in the dining room. If you have a “Christmas” cactus, its blooming is not far behind. Thanksgiving cactus (Schlumbergera truncata) and Christmas cactus (Schlumbergera x buckleyi) are popular, fall- and winter-flowering houseplants. Thanksgiving, Christmas and Easter Cacti have been kept as holiday plants since the 1800’s. These plants produce a wide variety of flower colors — red, rose, purple, lavender, peach, orange, cream, and white — depending upon the species. Schlumbergera species grow as epiphytes among tree branches in shady rain forests in Brazil. The ancestors of today’s Christmas cactus were discovered in southeast Brazil in 1819. Their pendulous stems make them a great choice for hanging baskets.
The first “holiday” cactus that was discovered in Brazil, Schlumbergera truncata, flowers in October and November. It is now called the “Thanksgiving cactus.” Another, Schlumbergera russelliana, found in 1837, blooms between February and April and became the “Easter cactus.” A hybrid of these two became the first “Christmas Cactus”(Schlumbergera x buckleyi). Besides flowering at different times, the leaves of each of these species of plants are slightly different. Christmas cacti have flattened leaves with rounded teeth on the margins as opposed to the Thanksgiving cacti that have pointed teeth. Easter cacti have pointed teeth with fibrous hairs in the leaf joints.
The Schlumbergera species is not a true cactus. It is not quite as drought tolerant as the name infers. However, it is a succulent plant and can store a reasonable quantity of water in the leaves. They can and do thrive for many years. It is not unusual for 40 or 50-year old plants to outlive their owners. They are often passed down to the next family generation, i.e. grandmother’s plant or Aunt Mary’s Christmas Cactus. These long-lived plants will develop what appears to be bark and reach a size of several feet with hundreds of blossoms during the annual flowering period.
All these holiday “cacti” have similar cultural requirements. They will keep their blossoms longer in cooler temperatures. They also prefer humid conditions. In the winter, our home atmosphere is often dry. One way to raise the humidity — just for your cactus — is to place the pot with its drip pan on top of a small container filled with pebbles. Pour water over the pebbles, but do not allow the water to rise above the bottom of the top layer of pebbles. The water will evaporate, increasing the humidity around the cactus. Keep the plant in a well-lit location away from drafts from heat vents, fireplaces, or other sources of hot air. Drafts and temperature extremes can cause the flower buds to drop from the plant before they have a chance to open.
Since Christmas cactus is a tropical type plant, it may, in fact drop flower buds if the soil gets too dry. The plants will wilt when under drought stress. Water thoroughly when the top inch or so of soil feels dry to the touch. The length of time between watering events will vary with the air temperature, amount of light, rate of growth and relative humidity. Dropping of unopened flower buds may be induced by an excessive number of buds or a sudden change in temperature, light, or other environmental factors.
Well-drained soil is a must for Christmas cactus. Use a commercially packaged potting mix for succulent/cacti plants or mix your own by combining two parts plain potting soil with one-part clean sand or vermiculite. Pruning your Christmas cactus after blooming will encourage the plant to branch out. Remove a few sections of each stem by pinching them off with your fingers or cutting with a sharp knife. These sections can be rooted in moist vermiculite to propagate new plants. The holiday cacti flower best when kept somewhat pot bound. Repotting is necessary only about once every three years and is best done in the spring. Inside the house, full sunlight is beneficial during fall and winter. Do not let temperatures rise above 90 °F once the flower buds are set in the fall. Continuous warm temperatures can cause flower buds to drop. Do not leave these cacti outside if temperatures will drop below 50 ºF.
Schlumbergera species are known as a thermo-photoperiodic plants. This means that formation of flower buds is dependent on a particular combination of day length and temperature. The same is true for Poinsettias. In the Northern Hemisphere these plants will begin the blooming process when the length of the day is approximately equal to the length of the night and when the temperature is in the range of 50 to 60 degrees F. Happy Gardening!