Every November the same plant shows up on grocery store shelves, in grandmothers’ kitchens and on half the windowsills in the country: the Christmas cactus, flat green stems tipped with flowers the color of a lit-up ornament. It’s about as familiar as a houseplant gets. And almost everything its name tells you is wrong.
It isn’t a desert plant. It doesn’t really bloom at Christmas, at least not most of the ones you can buy. And in the place it comes from, nobody calls it a Christmas anything.
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A cactus that lives in the clouds
The genus is Schlumbergera, a handful of species found only in the coastal mountains of southeastern Brazil, in the states of São Paulo, Rio de Janeiro, Minas Gerais and Espírito Santo. Warm, wet air off the Atlantic hits those mountains, rises, cools and condenses, which makes for some of the foggiest forest on the continent. (We have a soft spot for that kind of weather.) The cacti grow up there at anywhere from about 2,300 to over 9,000 feet, perched on moss-covered branches or tucked into rock crevices in little pockets of rotted leaves. The botanist David Hunt described collecting them in cloud and drizzle, with nights dropping below freezing.
So it’s a cactus with no spines and no leaves, just jointed green pads doing all the photosynthesis, that lives like an orchid in a cloud forest. Once you know that, most of its care makes sense. It wants shade and humidity. It hates being baked and it hates being drowned.
Our favorite detail is the name. In Brazil the plant is called flor de maio, the May flower. It blooms in the same season there as it does here, the turn from autumn toward winter, but on the far side of the equator that season lands in May. Same plant, same instinct, opposite calendar!
Darkness is the switch
What actually tells a holiday cactus to bloom isn’t the holiday. It’s the length of the night. Buds only form after the plant gets at least 12 hours of unbroken darkness, and researchers found that about eight days of 16-hour nights at around 61°F is enough to set them. Cooler weather slows the process down but also does something lovely: when buds develop below about 57°F, white and yellow varieties blush pink, and pink and red ones deepen.
That’s why the old advice to starve a cactus of water to make it flower doesn’t hold up. Studies have shown it’s simply incorrect. The trick is closer to the opposite of what a houseplant usually gets: put it somewhere the lamp never comes on at night, like a spare room or a cool, bright window you don’t sit near after dark, and let the long nights of November do the work.
Built for hummingbirds
Look at one of the flowers from the side and you can see who it was designed for. The petals fold back into a long tube with a chamber of nectar at the bottom, the stamens and a dark red style reach out past the mouth, and the colors sit at the red end of the spectrum. Every bit of it is tuned to hummingbirds, which hover in, drink, and leave dusted with pollen. Most species can’t pollinate themselves and need a bird to carry pollen from one plant to another. In many varieties the outer petals and inner petals are shaped differently enough that it looks like a flower blooming out of another flower.
The fruit is a bird’s job too. It doesn’t split open on its own. Birds eat it, and they’ve been seen wiping sticky seeds off their beaks onto tree branches, which is a fairly perfect way to plant a cactus that lives on trees.
Christmas, Thanksgiving, or something else?
Here’s the part that settles family arguments. Most of the “Christmas cacti” sold in the US are really Thanksgiving cacti, the group bred mostly from Schlumbergera truncata. You can tell by the stems. Thanksgiving types have sharp, pointed teeth along the edges of each segment, hold their flowers out roughly level, and carry yellow pollen. The true Christmas type, Schlumbergera × buckleyi, has rounded, scalloped edges, flowers that hang downward, and pink pollen. It usually blooms a few weeks later.
Even The Sill says as much: its listing notes that the holiday names are really about bloom timing, and if you look closely at the stems on their Christmas cactus, you’ll spot the telltale claws.
That original Christmas cactus was a cross made on purpose in England by a gardener named W. Buckley, first recorded in 1852, and by the 1860s Victorians were growing dozens of varieties in heated greenhouses and parlors. The plant fell out of fashion in the early 1900s and many of those old varieties were lost. Breeders picked it back up in the 1950s, and today American growers time millions of plants to be in bud for Thanksgiving week. One Dutch nursery alone was turning out two million a year by 1989. In Russia they skip the holidays entirely and call it dekabrist, the Decembrist.
The houseplant people pass down
There’s one more reason this plant ends up in so many grandmothers’ kitchens. It lives a very long time, and it’s ridiculously easy to share. Twist off a piece one to three segments long, let the broken end dry for a few days, and set it in loose potting mix. It roots in a few weeks.
So families do exactly that, for generations. A woman in Bozeman, Montana keeps a cactus that once belonged to her great-great-great-grandmother, who is said to have carried it west in the 1860s; when the local paper wrote about it in 2009 it was around 145 years old, and relatives all over the family have cuttings of it. A convent in Fargo has one past its hundredth birthday. Plenty of people reading this probably have a cutting from someone’s plant on a sill right now. It’s one of the only houseplants that comes with a family tree!
Keeping one happy
Think cloud forest, not desert. Give it bright, indirect light, since too much direct sun turns the stems reddish. Keep the soil just barely moist all year rather than letting it swing between soaked and bone dry, and use a small pot with a free-draining potting mix. Keep it out of cold drafts and away from heaters; sudden temperature swings are the classic reason a plant drops its buds right before they open, and it doesn’t like anything colder than about 50°F.
And it’s pet-safe, which matters this time of year, when so many holiday plants aren’t. If the cat chews everything, The Sill keeps a whole shelf of pet-friendly plants to keep it company.
A cactus on the holiday table, and one beside a little living Christmas tree. Photos: The Sill
If you want one
The Sill’s Christmas cactus
The Sill, the New York plant shop, sells a pet-safe Christmas cactus potted in a ceramic planter in your choice of color, or in a plain grow pot if you’d rather pick your own planter. A smaller size arrives November 9 and is open for pre-order now. Each plant can arrive in bud, in flower or neither, and it may well be a Thanksgiving type in Christmas clothes. One honest catch: it can’t ship to every state, including ours here in Oregon.
- November 20 to December 4: The Sill’s Black Friday and Cyber Monday sale, up to 50% off plants, planters and plant care gear.
- December 5 to 8: a short holiday plants sale, live trees included.
If you’d rather start with something even harder to kill, our ten houseplants for people with a knack for killing houseplants still holds up. And if you’ve ever suspected your plants are quietly moving when you’re not looking, you’re right; our time-lapse roundup of houseplants in motion proves it.
Sources: Edward F. Anderson, The Cactus Family (Timber Press, 2001); A.J.S. McMillan and J.F. Horobin, Christmas Cacti: The Genus Schlumbergera and Its Hybrids (1995); Encyclopaedia Britannica; University of Tennessee Extension; Bozeman Daily Chronicle; The Forum of Fargo-Moorhead.
