One long-ago November, the library staff received a gift from two grateful patrons. This small, but sincere, token of appreciation grew in a four-inch pot. I put it on the windowsill for all to see and cared for it out of respect for the givers’ kindness. Soon it grew and grew, in size and beauty, until it became a holiday favorite of our patrons.
Each year, like clockwork, our beloved “Christmas cactus” produces spectacular blooms . . . at Thanksgiving. This year I wondered why and began to research the topic. Did the bloom time depend on care? The age or health of the plant? The variety? What is a Christmas cactus in the first place? The concise answer is that several different species are marketed as Christmas cactus, though the one most commonly sold, Schlumbergera truncata, is actually a Thanksgiving cactus. The true Christmas cactus, Schlumbergera x buckleyi, is a hybrid that was created by crossing the Thanksgiving cactus with another species back in the 1840’s. The article “False Christmas Cactus” from the Nebraska Extension service, clears up some of the confusion.
So, I set out to confirm our plant’s identity once and for all. By observing the following features, you could identify your plant, too.
The most obvious difference between the two plants is their bloom time. True to form, the Thanksgiving cactus blooms in late November while the Christmas blooms about a month later.
To further distinguish between the two species, it helps to know a little about their anatomy. Although these holiday cacti aren’t spiky desert plants, they are indeed members of the cactus family. Like other cacti, they lack leaves. The flattened green segments are actually modified stems called phylloclades which function as leaves by performing photosynthesis. One way to distinguish between Christmas and Thanksgiving cacti is to compare the margins of these segments. The Thanksgiving cactus will have pointed teeth; teeth on the Christmas cactus will be more rounded.
Pointed Teeth of Thanksgiving Cactus
The angle of the flower also separates the two species. According to the North Carolina Extension Gardener, the blooms of the Christmas cactus “droop down toward the ground.” The Real Dirt Blog has two nice images which illustrate this.
Christmas Cactus,Schlumbergera buckleyi
Wayne Ray User:WayneRay, Public domain, via Wikimedia Commons
As you can see from our lead photo and the image below, the blossoms of the Thanksgiving cactus are horizontal or slightly upturned.
Blossom of Thanksgiving Cactus
Another way to differentiate them is by the color of the anthers and pollen: shades of pink and purple for Christmas; yellow for Thanksgiving.
Anthers with Pollen on Thanksgiving Cactus
When I finally felt confident that our cactus was the Thanksgiving (truncata) species, I read that the Christmas hybrid “is rarely for sale.” Oh, well. I could have saved some time and trouble but, then again, it’s good to look closely.
Given that most of us own Thanksgiving cacti, the next question is, “Why do some of them bloom much better than others?” For years I have sworn that I don’t give any special care to the library’s plant. This is only half true. It turns out that this plant’s location contributes to its floral success. The World of Succulents says that these “short-day plants” need at least six weeks of “darkness and cool temperatures” in order to form buds. At home, my plants vacation on a shady patio until the nights get chilly. When nighttime temperatures drop to the low 50’s (40’s?), they move to an unheated basement until buds form. Then I invite them upstairs!
The library’s Thanksgiving cactus experiences similar circumstances. At night, it sits by a cool window in a room with the heat turned down. The lights go off at 8:00 p.m. or earlier. Every autumn night is a long night for them.
Year-round care for this species can be improved by knowing something about their natural history. The genus Schlumbergera is native to the coastal mountains of southeastern Brazil. These species live in “high altitude, moist forests where conditions are relatively cool, shaded and humid” according to “Cactus from the Rainforest: Christmas Cactus.” What this means is that they need bright, indirect sunlight and moderate temperatures – like the north-facing window in the library’s air conditioned building. When the plants are exposed to too much sunlight, their phylloclades turn red. They appreciate an occasional outdoor shower.
Schlumbergera truncata
(c) Victor Hugo Rebecchi Siqueira, some rights reserved (CC BY-NC)
It’s also important to note that these are epiphytes (living on tree limbs) or lithophytes (living in rock crevices). They don’t normally grow in the ground. While these cacti appreciate humidity, they don’t like wet feet. Allow the soil to dry down in between waterings. When repotting, use a fast-draining mix, but realize that these plants prefer to be potbound. The pot at the library is so full of roots that there’s little room for soil. Consult the Napa Master Gardener Column for detailed advice about their care and propagation.
After its holiday performance, our Thanksgiving cactus will need some R & R. With some very minimal care it could live 50 years or more. I’d better train a protege!
