Thanksgiving and Christmas Cacti

By

Paula Szilard


If they weren’t so common, we’d all be transfixed by these stunning plants, but alas, familiarity still breeds contempt, even in our interaction with plants.  Thanksgiving and Christmas cacti are rainforest cacti from Brazil in the genus Schlumbergera (formerly Zygocactus).  They were introduced into Europe in the early 19th century by Allan Cunningham, a collector for Kew Gardens.  In 1858 this genus was named after Frederic Schlumberger, a French collector of cacti.   There are six species, but most are now rare in cultivation. Most of the plants we grow in our homes are hybrids


The Easter cactuses are distinct and fall into two different genera-- Rhipsalidopsis and Hatiora.  The Rhipsalidopsis stem segments have a more oval and less jagged appearance than those of Schlumbergera.


There are over 200 cultivars in all permutations of pink, red, peach, coral and white.  There supposedly are yellow varieties, but they are more of a peachy yellow than a true yellow.  There seems to be some ambiguity in the in the assigning of colors.  I suppose that if a color is hard to achieve and a breeder has been working for years to breed a yellow flower, for instance, then even a yellowish peach looks like a real yellow!


Schlumbergeras have flattened segmented stems (phylloclades) resembling leaves, with zigzag edges and prominent midribs.  They are cacti, of course, as evidenced by their areoles. These areoles, located in the notches of the Schlumbergera leaf margins, are depressed areas (raised in some cacti) where the spines, branches and flowers emerge. Schlumbergeras really do not have spines, but tiny, barely visible bristles in the areoles. This is where the flower buds are formed.


Basic Care

If you are the recipient of one of these lovely long-lived beauties, consistently good care can eventually turn this plant into a family heirloom.  , There are many stories of ancient plants that have been handed down in the family.  Elvin McDonald, author of dozens of houseplant books and founder of the Gesneriad Society, recounts having done a survey for a newspaper article which unearthed many such plants, including one that was reported to be 120 years old and one supposedly over a hundred years old that was growing in a 30-inch butchering kettle and measured 16 ½ feet in circumference and 5 feet in diameter with more than 1000 blooms each year.  Such plants are definitely worth passing down!


Yet the care these plants require is fairly straightforward.  They do best when potted up in a peat based mix, not a cactus mix. That is what the growers use. I have had success with Fafard #2 and with plastic pots. These are after all rainforest cacti and the stem segments (phylloclades) function as leaves, so they need a medium that retains water.  Remember, you are essentially dealing with a “leafy” plant.  Fertilizing is best done with a balanced, water soluble fertilizer with an NPK ratio of 20-20-20 or something close to those numbers.  Many people fertilize as little as 2-4 times a year and avoid fertilizer build-up in the growing medium by periodically leaching out the fertilizer with plain water.  


Place your plant into very bright shade, avoiding any direct sun.  Water it well from spring to the conclusion of the flowering period, keeping the mix consistently moist, but not soggy.  This is the time of year when the stems grow most actively, and they need more water. Then you can ease up a bit, watering only enough to keep the medium from drying out until early spring, when you again resume regular watering.  Keep the mix moist, but never allow the pots to stand in water.   You may place the plant into a bright shady area for the summer (under a tree, for instance), as long as you slowly acclimatize it to this new environment.


Blooming and Reblooming

When it comes to getting these cacti to bloom, there are a lot of old wives’ tales circulating. One such tale is to allow the plant to dry out completely. This is not a nice thing to do to a rainforest plant and can lead to its demise. Another is to put it into a closet like a poinsettia.  This is not very helpful either because most of us can’t remembers to remove the plant from the closet and put it back each day.


Schlumbergeras bloom in response to both day length and temperature.    More specifically, when room temperatures are above 60 F they bloom during short days and long nights of fall and winter.  At these temperatures they need 12  hour days and nights without even a smidgeon of artificial light.  This is where some people got the idea of putting these plants into a closet.  Alternatively, when temperatures are 59 F or below, day length and exposure to artificial light are immaterial.  The plant flowers in response to temperature alone.  If temperatures fall to 55F and below, plants may show more lavender and pink coloration.


My plants in the kitchen have always flowered although they were right under a light that was on every evening until bedtime.  The interesting thing is that they bloomed better before we had our cold, leaky windows replaced.  They still bloom, but they could bloom more prolifically.


So, while it is next to impossible for people to rebloom their poinsettias because they do have to shield them from all artificial light, it’s fairly easy to rebloom a Thanksgiving or Christmas cactus simply by putting it in a cool place.  In our usually frigid fall and winter weather, most of us have a cool enough spot near a leaky window, in an enclosed porch or in an unheated room.


A Few More Pointers

There’s just one more problem in relation to blooming.  Plants sometimes seem to experience bud or flower drop.  This can be the result of temperatures above 80F or below 50F, insufficient light, a dry or overly wet potting mix, and exposure to ethylene gas. The gas can come from sources in the home such as fireplace or even a fruit bowl.  Once a cactus has formed buds in one location, be careful when you move it.  The buds have oriented themselves to face the light.  If you move it to another location, make sure they are again pointing toward the light, otherwise they will be turning in the opposite direction. The buds may then become weakened and might drop.


Pruning is only necessary to control growth, increase branching and enhance the shape of the plant.  If you decide your plant needs pruning, then prune it just after flowering or wait until spring.  Twist off enough segments to enhance and even out the shape of the plant.


Some authorities recommend annual repotting, although this is probably not necessary.  If your plant needs repotting, then this is also best done after flowering.  Move the plant up to the next size pot, no larger.  These cacti do not have large root systems and unnecessarily large pots can promote root rot and similar problems.



Sources:

The Ball Redbook, 16th ed.  Batavia, IL, Ball Publishing, 1997.


Cobia, Mark E.  Zygocactus (Schlumbergera):  a Comprehensive and Practical Guide for the Weekend Gardener.   Coffs Harbour, Australia:  Tillington House, 1992.


McDonald, Elvin.  The New Houseplant:  Bringing the Garden Indoors.  New York:  MacMillan, 1993


Nell, Terril A.  Flowering Potted Plants:  Prolonging Shelf performance:  Postproduction Care and Handling.  Batavia, IL:  Ball Publishing, 1993.