Jennifer Schultz Nelson
Extension Educator, Horticulture
Christmas cactus is a lesser known holiday plant compared to the poinsettia, but no less spectacular in my opinion. Their flowers are truly unique, and unlike poinsettia, it is relatively easy to coax a Christmas cactus into re-blooming each year.
Christmas and Thanksgiving cacti, commonly called 'holiday cacti' are named all in reference to the time of year they typically bloom. These cacti are each of different species, but all of the holiday cacti are in the genus Schlumbergera. An older name that you still see in stores occasionally is Zygocactus.
The flowers produced by holiday cacti are all similar, trumpet like with layers of petals curving back as the flowers open. Typical colors are white, and shades of pink, purple, reds and salmons. Occasionally you may see yellow. 'Gold Charm' is a yellow-flowered cultivar that is really beautiful. There are some cultivars available with modified flowers that have frills or ruffles on the petals.
The Christmas Cactus' native environment is tropical, not desert like the name "cactus" suggests. Christmas cactus and the other holiday cacti are native to the Organ Mountains in Brazil. They are forest cacti that are used to growing in the lush understory of tropical forests.
These cacti are a bit different in appearance than the "typical" cactus, lacking the sharp spines usually associated with cacti. Given their native habitat in tropical forests, they can tolerate more water than you might expect, storing it in their succulent stems. However, too much water will cause root rot to set in. At the other extreme, too little water will cause wilting, flower bud drop and even death of the whole plant in extreme cases.
Unlike their desert relatives, these cacti cannot tolerate intense full sun. Full sun will actually burn the leaves. They perform far better under indirect but bright light.
Christmas cactus will be happy in typical winter home temperatures, but a cooler location (50 to 55 degrees) will allow flowers to last longer. In summer place the plant outdoors in a sheltered location that receives bright indirect light if at all possible.
As a rule of thumb drafts, sudden changes in lighting or watering schedules may cause a Christmas cactus to drop unopened flower buds. If you have to change the environment of a Christmas cactus, do it as gradually as is reasonably possible.
Most Christmas cactus seem to do better when a little root-bound in their pot, but if you feel you must re-pot, use a potting mix that is well-draining, such as a mix designed for cactus. To me, some of the commercial cactus mixes are a bit too sandy for Christmas cactus, so I have been known to deliberately mix in at a bit of general purpose potting mix to increase the organic matter in the mix slightly. I would recommend about two parts cactus mix to one part general purpose potting mix if your cactus mix is very sandy. The mix is still well-draining, and the Christmas cacti seem to do very well.
Christmas cactus is also a great pass-along plant. The stems grow with distinct joints, and can be easily separated. If you let the broken end dry out for a day or two, then plant it in a pot of its own, it will root readily. Planting multiple segments in one pot will help produce a fuller looking display and will not hurt the individual plants one bit.
I have heard from people who have had the same plant in their family, or descendents of the same plant for over one hundred years. A friend gave me a gift a couple of years ago of a plant started from the plant her great-grandmother grew. These really are plants with longevity, not disposable plants like some blooming houseplants seem to be.
The question I get often is how to get the Christmas cactus to re-bloom. It can be really easy, or really tedious, it just depends how much time you want to devote to the effort.
I stumbled on the secret that convinced my own Christmas cactus to produce tons of flowers. My first plant, purchased while I was in high school, had occasionally thrown out a bloom or two in the years after I bought them, but it was nothing really impressive. I read about the plant needing twelve hours of darkness each day for 6-8 weeks and was discouraged, knowing in all likelihood I'd have trouble remembering to keep that schedule.
That same plant purchased in high school was still alive and kicking when I was in graduate school at the University of Illinois. I typically placed my Christmas cactus out on my apartment's balcony along with my other houseplants each summer.
When the fall semester had started, the weather turned cooler, and I was too busy to bring my houseplants, including the Christmas Cactus, in from their summer outdoors. When I finally brought the plants in on a night when a freeze was predicted, I noticed the Christmas Cactus was covered in flower buds. Not just a few, but the end of every arching branch had one or even two buds.
It turns out that the cooler and longer nights of early fall are the environmental trigger for flower development in the Christmas Cactus. Cooler nights (50-55 degrees) actually eliminate the need to have a rigid light/dark schedule. My forgetfulness actually paid off for once!
Check out more University of Illinois Extension information about Christmas Cactus at: http://www.urbanext.uiuc.edu/trees/flowersgreen.html.