Even reference sources differ on the specifics of holiday cactus nomenclature. The experts at Clemson University identify Thanksgiving Cactus as a single species, Schlumbergera truncata, Christmas Cactus as Schlumbergera bridgesii and the closely related Easter Cactus as Hatiora gaertneri. English botanist Martyn Rix identifies Christmas Cactus as a hybrid, Schlumbergera x buckleyi, originally created in the 1840’s by a man named Buckley who crossed Schlumbergera truncata with Schlumbergera russelliana to create the progenitors of the modern hybrid Christmas cactus.

All holiday cacti are very similar, except for bloom times. They are native to areas of Brazil near Rio de Janeiro, where they live as epiphytes, non-parasitic plants that flourish in trees, deriving sustenance from air, water and debris that collect around them. This is good news for those of us who love them, as they don’t need the bright sunlight required by terrestrial cacti. They also do not have the sharp spines of some of their relatives in the true cactus or Cactaceae family.

The vast majority of holiday cacti are sold growing in soil-like potting mix. What they really need is excellent drainage, not to mention caretakers who refrain from flooding them with water every day. Overwatering—which means watering before the soil is dry to the touch—can result in potentially fatal rot. If your holiday cactus is not thriving, cut back on water and repot it in a mixture of about 40 percent perlite—available at garden centers—and 60 percent fresh potting mix. Those who hate repotting plants can take comfort in the knowledge that holiday cacti bloom best when they are slightly potbound
and only need repotting every three or four years.

All holiday cacti should come in before nighttime temperatures begin falling below 50 degrees Fahrenheit. Sometimes, if the plant undergoes dramatic temperature changes, flower buds will drop off. There is not much to be done, other than avoiding extremes the next time. Fertilize with a balanced, water-soluble houseplant fertilizer diluted to half strength. Stop fertilizing in late summer to encourage flower formation in Christmas and Thanksgiving cacti. Resume about a month after the flowers have bloomed.
Source: gardenersapprentice.com found at https://worldofsucculents.com/christmas-cactusconfusion/ This article appeared in the GCN’s December 2018-January 2019 Newsletter.