Every year about this time, stores of all sorts sell something called Christmas Cactus, a showy plant with segmented foliage that arches out over the sides of the pot. Since most people find the foliage relatively unimpressive, the seasonal specials are always sold in bud or with newly-opened flowers. The long, tubular flowers, which appear at the ends of the stems, are made of many slender pointed petals fused at the bases. Flower color ranges from white to shades of peach, orange, purple, rose, and red. Bi-colored varieties are also widely available.
Sometimes merchants trying for early sales offer the similar-looking Thanksgiving Cactus starting just after Halloween. To the casual buyer, these are dead ringers for Christmas Cactus and also closely resemble the Easter Cactus sold in the spring. To make matters a little more complicated, the various Holiday Cacti are all sometimes sold under the exotic-sounding name Zygocactus.
So what is up with all of these Holiday Cacti? Is it all marketing, or are they different plants? More to the point, if those showy blossoms seduce you, will your Thanksgiving/Christmas/Easter cactus survive for more than a few weeks? Southerners, especially older ones, will sometimes tell tales of family Christmas Cacti that have survived for generations. But are they talking about the same plants that now grace thousands of big box stores?
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, created in the 1840s by a man named Buckley, who crossed Schlumbergera truncata with Schlumbergera russelliana to create the progenitors of the modern hybrid Christmas Cactus.
What does all this mean? For the average person, absolutely nothing. However, those who have nurtured ancestral Christmas Cacti for decades can rest assured that their holiday plants are essentially the same as the specimens that today's urban sophisticates buy in funky shops to decorate their minimalist apartments. All Holiday Cacti are very similar, except for bloom times. They are native to areas near Rio de Janeiro in Brazil, where they live as epiphytes, non-parasitic plants that flourish in trees, deriving sustenance from the air, water, and debris that collect around them. This is good news for those of us who love them, as they do not need the bright sunlight required by terrestrial cacti. They also do not have the sharp spines of some of their relatives in the Cactaceae family.
The vast majority of Holiday Cacti are sold growing in a soil-like potting mix. However, they need excellent drainage, not to mention caretakers who refrain from flooding them with water daily. 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 the water and repot it in a mixture of about 40% perlite, available at garden centers, and 60% fresh potting mix. Those who hate repotting plants can take comfort in knowing that Holiday Cacti bloom best when they are slightly pot-bound and only need repotting every 3 or 4 years.
All Holiday Cacti should come in before nighttime temperatures fall below 50 °F (10 °C). Sometimes, flower buds will drop off if the plant undergoes dramatic temperature changes. 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 Cactus and Thanksgiving Cactus. Resume about a month after the flowers have bloomed.
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