The Gardener's Apprentice

Holiday Cactus
Holiday Cactus

Christmas Cactus Confusion

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 blooms.  The long, tubular flowers, which appear at the ends of the stems, are made up of many slender, pointed petals fused at the bases.  Flower colors range from white through shades of peach, orange, purple, rose and red, with bi-colored varieties 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 bear a close resemblance to the “Easter Cactus” sold in the spring.  To make matters just 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 you are seduced by those showy blossoms, 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.  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, and Christmas cactus as Schlumergera bridgesii.  The closely related Easter cactus has a completely unpronounceable name, Rhipsalidopsis 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 the truncata species with another Schlumbergera to create the progenitors of the modern hybrid Christmas cactus.

What does all this mean?  For the average person—absolutely nothing.  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 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 pot-bound and only need repotting every three or four years.  I repotted mine after five, but chose a pot that was only slightly larger than the old one.  The plant rewarded me this fall with a host of pink and white blossoms.

My cactus, which is probably the Thanksgiving type, lives in a south-facing window during the cold weather months.  It gets an outdoor vacation along with its other houseplant cronies during the growing season.  I let it sit in very light shade, to which it seems partial.  Due to laziness, I let it stay out until at least October 15, which suits it very well.  Bud formation is stimulated by increasing hours of darkness, so Mother Nature does the job that I would probably be too indolent to do myself if the plant lived indoors full time.  The only caveat to this Lazy Woman’s Formula for Plant Success is that 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.  I try to fertilize whenever I water during the growing season.  Stop fertilizing in late summer to encourage flower formation in Christmas and Thanksgiving cacti.  Resume about a month after the flowers have bloomed.

All of the holiday cacti are lovely in flower.  I am especially fond of ‘Aspen’, a Christmas cactus with frilly, white flowers that appear almost orchid-like.  Each blossom sports a white ring around the throat.  If I can consolidate some of the ten thousand pots of geraniums currently occupying my indoor growing area, I may just acquire one.

Holiday cacti are widely available in garden centers and other retail outlets.  For a wider selection, try Logees Greenhouses, 141 North Street, Danielson, CT 06239, www.logees.com, (888) 330-8038.  Free catalog