Holiday cactus, Thanksgiving cactus, Christmas cactus, Easter cactus, Zygocactus, Schlumbergera … whatever what the heck you call them, they’re all absolutely lovely and I’ve fielded quite a few questions about them this year. Maybe it’s time to chat about how to keep them thriving instead of subsisting, and, while we’re at it, get that whole naming problem out in the open.
- First, let’s clear up the name thing. Zygocactus is a former genus name of the so-called Christmas and Thanksgiving cacti, so you won’t hear these plants called that much anymore – and if you do, it’s inaccurate. Schlumbergera is the current genus. It contains six to nine species, because taxonomists are still waffling a bit on whether or not the (former) Hatiora genus should be amalgamated into Schlumbergera. Collectively naming these plants “holiday” cactus reflects the times of the year they typically – but not always – bloom (and then we can quibble – as I’ve seen in some gardening groups on Facebook – about whether they burst forth in flower in time for the Canadian or American Thanksgiving and it all gets positively silly). What we call a Thanksgiving cactus is Schlumbergera truncata, and it features crab- or claw-like hooked appendages on its flat stems. The flowers also tend to be more erect than those of the so-called Christmas cactus. The Christmas cactus (S. x buckleyi), a hybrid of S. truncata and S. russelliana (which has super long segmented stems), has scalloped edges on the stems. And, finally, Easter cactus (S. gaertneri, formerly Hatiora gaertneri), which is somewhat
impossiblemore challenging to acquire for purchase in this neck of the woods, has defined rounded edges on the flat stem segments. S. truncata (Thanksgiving) seem to be the most overwhelmingly available species for sale here, so if you have a friend who has a true Christmas or Easter cactus, see if they’ll give you a cutting for a box of chocolate truffles or something lovely like that.
- Another ID tip? Thanksgiving cactus (S. truncata) has yellow pollen, while Christmas cactus (S. x buckleyi) has pink pollen.
- Curious about that defunct old genus name, Zygocactus? It refers to the fact that the flowers of Christmas and Thanksgiving cacti are zygomorphic – that is, bilaterally symmetrical (possessing two dissimilar halves). Another common plant with zygomorphic blooms is a viola.
- So … why do holiday cactus bloom when they do? It all has to do with photoperiod. The chillier temperatures and longer nights of autumn and winter trigger Thanksgiving and Christmas cactus to bloom. They need at least 6 weeks (give or take) of short days and uninterrupted 13 to 14 hour nights to make a colourful splash. Easter cactus take a bit longer – they need at least 8 to 12 weeks (give or take) of uninterrupted 13 to 14 hour nights to decide it’s time to bloom. (What do I mean by ”uninterrupted”? The plants must be in darkness for 13 to 14 hours per day for the prescribed time to bloom. Both artificial light and sunlight can disturb this period of darkness, and influence whether the plants bloom or not.) And … sometimes Thanksgiving and Christmas cactus will joyously offer up another kick at the can in late January or early February and rebloom. (This second flush of flowers isn’t usually as abundant as the earlier one, but it’s equally appreciated.)
- I’ve heard some stories about people stuffing their Schlumbergera spp. into a dark closet or a basement room to get them to bloom. If you want to control the timing of the bloom period, you can put the plants in darkness for 14 hours each day for several weeks to force them into bloom. But you still need to take them out so that they get some light and holiday cactus really don’t like being moved. So unless you have the equivalent of blackout curtains for your plants and can keep them in one place, I’d recommend letting things happen naturally. To that end, see #4 above, and leave your closets to house non-plant things.
- In Brazil and other parts of the southern hemisphere, most Schlumbergera spp. bloom in May or thereabouts. So there go the common names we northerners have attributed to the plants.
- Schlumbergera don’t have leaves. Those beautiful green stems perform all the photosynthesis the plant needs.
- Those little hooked appendages on the Thanksgiving cactus? They’re called cladophylls. Use that at your next trivia night!
- Three feet is the approximate maximum stem length of a Christmas cactus (S. x buckleyi). (But, again, give or take. It all depends on how delighted the plant is with its surroundings and how much love you lavish upon it.)
- There are apparently over 200 cultivars of S. x buckleyi (Christmas) cactus, which represents a staggering array of flower colours! It’s tempting to want to start a massive collection ….
- Schlumbergera spp. are native to the rainforests of Brazil, which means they aren’t like other cacti, which thrill to hot, dry climates. Like many tropical plants, they prefer dappled light, and a temperature consistently hovering around 20°C (68°F).
- Many Schlumbergera spp. are epiphytic, which means in their native habitat, they like to hang out in trees. Like, literally. Some species are epilithic, and they grow on rocks.
- Holiday cactus don’t need a lot of water, as befitting a cactus, but they will suffer if they aren’t watered sufficiently. Don’t forget about them. Make sure you give them a glug of H20 about 3 times per month. Test the soil with your finger before watering – if the soil is damp, wait a little while. If it is bone dry, haul out the watering can. Don’t get the crown of the plant wet, as this may induce rotting. Don’t withhold water while the plants are blooming, but don’t overwater them, either.
- You don’t need to fertilize your holiday cactus year-round – stick to spring and summer feedings, when the plants are actively putting out green growth. Use a balanced liquid soluble fertilizer, or fish emulsion or liquid kelp once per month.
- Keep the plants out of direct, bright light in the summertime – remember that the native habitat for many of them is in the canopies of trees.
- Holiday cactus like being a little pot-bound. While the average lifespan of a holiday cactus is 20 to 30 years, you’ve undoubtedly seen the photos on the ‘net of the 50-year-old plants that seem to be busting out of their pots and blooming like they haven’t a care in the world. That’s because they are happy in cramped quarters. I’ve seen recommendations to repot them every three years or so but you can usually go quite a bit longer, unless the plants give you an indication that their abode is simply no longer suitable. (You’ll know it’s time when they call your realtor and request a little ”for sale” sign. Um, no. They’ll actually start acting up – watch for behaviours like wilting, suddenly needing more water than usual and more frequently, or perhaps the stems will begin to shrivel.)
- I usually just use a commercial potting mix for my holiday cactus, but a succulent or cacti mix is also suitable. Don’t forget to follow a yearly fertilizing schedule (see #14, above).
- Propagating Schlumbergera is easy and fun! If your cat hasn’t already knocked the plant over and dislodged a segment or six, just neatly cut off a length of 2 segments with a clean pair of scissors or a sharp knife and set the chunk out on a piece of towel for three days or so to callous over. Then put some damp potting soil in a small container and plop the cut piece an inch or so into the medium, newly-calloused side down. Keep the soil evenly and regularly moist, and after a few weeks, the little cutting should root nicely. Why not propagate some cuttings early in the year for holiday gifts for your friends and family come Thanksgiving or Christmas? Chocolate truffles of gratitude may be in your future! 😉
- Are the stems on your holiday cactus turning red? While this may look festive and pretty, it’s usually a sign that the plants are getting way too much direct light. Offer them a bit less for bliss.
- Wrinkled stems? You’re either overwatering or underwatering … this is evidence of either issue. Make some small adjustments to your offerings of irrigation until the situation improves.
- Bud blast is a huge problem for holiday cactus. Your plants may form flower buds on the tips of the stems, and you’ll get all happy and excited at the prospect of tons of blooms, then all of a sudden, you realize that stuff just ain’t happening. The plant has decided to sulk – maybe it just doesn’t want you to show it off on Instagram this year. There are a few reasons why bud blast occurs, but the big one is that you probably inadvertently moved the plant at some point over the past month or year or decade and it now hates your guts. That’s a bit of an exaggeration, but do try not to move the plant (or even turn the pot) while it is forming buds, and you should be rewarded. Changes in temperature, moisture levels, or light can also trigger bud blast.
- What if your holiday cactus doesn’t bloom at all? If you’ve just propagated some cuttings, the new plants won’t usually bloom for a year or two – they’re simply too young. Very ancient plants sometimes don’t bloom as well. Plants that have not received enough nutrients throughout the year may fail to bloom. And finally, consider if you’ve changed the obvious things, like temperature, light, or how much water the plants have been given.
Do you grow Schlumbergera spp.? Feel free to post a link to photos of your plants, if you wish!
Thanks for this excellent info! Enjoyed it plus learned a lot (and now I know why I got only one bloom lol).
I have owned a rather large Christmas cactus for some 20 years and it was pretty large when I got it. I practice almost total neglect (only water it occasionally) and it has bloomed profusely every year. I have never repotted it. Never fertilized it. Only moved it twice, to new residences. Beats the heck out of me why it’s still going strong.
Fascinating! I love all those beautiful scientific words and names. I think I am an epiphytic at heart! Happy New Year Sheryl!
Excellent article! Thank you!