Christmas vs. Thanksgiving cactus

In the Garden

Ralph Purkhiser, Purdue University Master Gardener


     I have recently had several people who have called, saying that their Christmas cactus is already blooming.  It is possible that it is not a Christmas cactus at all, but rather is a Thanksgiving cactus.  I have done a lot of research on university websites and websites of plant breeders and the biggest thing I have learned is that the issue is confusing at best.  There is a lot of contradictory information out there.

     One thing is certain.  Both Christmas and Thanksgiving cacti are true members of the cactus family in the genus Schlumbergera.  Most of the sites agree that the Thanksgiving cactus is Schlumbergera truncata (sometimes spelled truncate).  Some sites identify the Christmas cactus as Schlumbergera russelliana, while others use the binomial Schlumbergera buckleyi.  Some say that Schlumbergera buckleyi is actually a cross between Schlumbergera truncata and Schlumbergera russelliana.  It can be quite confusing.

     However, just referring to them as Christmas and Thanksgiving cacti clears it up a bit.  There are some differences on which everyone seems to agree.  Both are native to the coastal mountains of South America, where they grow as epiphytes in trees.  Both have flat stems composed of segments known as phyllocades.  A major difference is that the edges of the Thanksgiving cactus segments have two to four serrations or teeth, while the Christmas cactus is smooth.  In nature, the Thanksgiving cactus blooms a few weeks earlier than the Christmas cactus, but since either can remain in bloom for up to 8 weeks, their bloom times may overlap.  Another difference is that the Thanksgiving cactus has yellow anthers (where the pollen is found) while the Christmas cactus anthers are purplish-brown.

     The blooms may also be affected by light and temperature.  In the fall, both cacti should be placed in a place with temperatures around 65 degrees F.  They need 12 to 14 hours of total darkness for about 8 weeks to set buds.  Many people resort to covering the plants with paper bags in the evenings to prevent artificial light pollution.  Once the buds are set, the plants may be moved into rooms with more light, but one should still avoid bright direct sunlight and cold drafts.

     When you buy or receive a holiday cactus as a gift, it will likely be wrapped in foil.  The foil is for decorative purposes, but is deadly for the plant.  Unlike desert cacti, the Schlumbereras need more water, but they do not like to be left soaked.  They need good drainage, so either remove that foil or cut holes in the bottom to let the water out.  If you set it in a saucer, water the plant until water drains out the bottom, but empty the saucer afterward.  However, some humidity is good, so one could put rocks in a saucer and leave the water, as long as the water does not touch the bottom of the pot.   Usually, the new plant will be in a plastic pot, but terra cotta is actually better for drainage.  If you decide to treat your plant to a new home, select a pot that is not much bigger than the one in which it came.  These cacti actually like to be a little pot-bound and do not need to be re-potted for three to five years.  They are not terribly picky about the potting soil, but it does need to drain well.  I prefer a cactus mix, adding some peat moss to give the plant more acid.

     If you take care, you can have your holiday cactus for many years.  I personally know someone who has a specimen that is over 30 and she says it has never been repotted.  She does cut it back a couple of months after it finishes blooming, causing it to branch and resulting in more blooming stems the following year.  The cuttings may be left to dry until the end scabs and then planted about an inch deep in moist potting medium.  A plastic tent will help keep the humidity up for better rooting.  New growth is the best indicator that the plant has rooted and is ready to add to your collection or be given to a friend.


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