Houseplant · Cactaceae
Thanksgiving Cactus
Schlumbergera truncata
Flat, toothed segments and bright pink and red blooms give this forest cactus its unmistakable look.
Bright indirect
50–86°F · 10–30°C
USDA 10–12
4–20 in · 10–50 cm
Overview
The Thanksgiving cactus is a forest cactus built from chains of flat, jointed segments rather than a single spiny column. It comes from the coastal mountains of Brazil, where it grew along tree branches instead of desert sand. In late fall, near Thanksgiving, those green segments tip into bright flowers, the payoff for a plant that trades desert spines for flat, pad-like stems.
The giveaway is in the edges. Each flat segment is rimmed with pointed, claw-like teeth, sharp little projections that curve like a crab's pincer and give the plant its crab cactus and claw cactus names. Its relative the true Christmas cactus is softer in outline, with rounded, scalloped margins on its segments, and it flowers about a month behind. Most plants sold as Christmas cactus wear these toothed edges and are really this species.
Up close this is an easy, long-lived plant whose flattened stems thicken and multiply over decades, flowering more heavily as it fills out. Its two real needs are steady conditions while the buds swell and the cool nights and short autumn days that set those buds. The color that follows is worth the patience.
Care
The short version: bright indirect light, a drink once the mix dries at the surface, and cool fall nights to draw out the flowers. Keep the roots slightly crowded, and once buds appear, leave the plant still.
Light
It shows its truest color in bright, indirect light, away from direct sun. Partial shade or a little soft sun does no harm, but harsh midday rays scorch the green segments to pale or red. Light from a window facing east or north keeps the pads a deep, even green.
Water
Let the top half of the mix dry before watering, then soak it through. The fleshy segments store some water, so it takes more than a desert cactus yet rots if left waterlogged. Once buds form, even moisture keeps them from shriveling and dropping.
Soil
Set it in a well-drained, organic-rich potting mix made for epiphytes, loose enough to drain fast while holding a little moisture at the roots. A slightly acidic pH of 5.5 to 6.5 suits it.
Temperature
The segments stay firm and green across a wide range, roughly 50°F to 86°F (10°C to 30°C). Fall is the turning point: cool nights and short days are the cue that brings on the buds.
Humidity
Average indoor air keeps the segments plump, so there is no humidity target to hit. A little extra moisture helps a fresh cutting take, though a grown plant stays firm without it.
Feeding
A monthly dilute balanced houseplant fertilizer through spring and summer keeps the new segments coming, then feeding stops in late summer to turn the plant toward flowering. It draws on more magnesium than most plants, which an occasional Epsom-salt solution restores.
Pruning
When the last flower fades, pinch or twist off a few stem segments at the joints. Each break pushes out new growth, and the plant thickens into a fuller, more branching mound of segments.
Repotting
Repot only every 3 to 4 years, since crowded roots push it to flower rather than sprawl. New roots creeping from the drainage holes, water sluicing straight through, and stalled segment growth all say it is time.
Size & spacing
It keeps a compact form, about 4 to 20 inches (10 to 50 cm) in height and spread, its flat segment chains spreading to the pot's edge. One plant is enough to drape a hanging basket or crowd a windowsill pot with green pads.
Troubleshooting
Most of what goes wrong shows on the segments themselves, as buds that drop or stems that turn soft and lose their green. Both come down to watering and where the plant sits. Match the look below, then correct the conditions.
Segments going soft, brown, and mushy at the base
Soft, blackening tissue at the base is root rot, the result of a mix that never dries. Cut back to firm growth, stripping the mushy segments and the brown, slimy roots, then reset the plant in a fast-draining epiphytic mix and water less. Prevention is simple: let the surface dry before the next soak.
Fix:
- Reduce watering frequency
- Repot into a fast-draining epiphytic mix
- Remove rotted segments and affected roots
Swelling buds wither and fall before opening
Bud drop is the plant recoiling from a change it disliked. After the buds set, it wants one settled spot, even moisture, and no drafts or temperature swings. Shift it to show off the color and the little buds dry up and drop within days, so leave it untouched until the blooms unfurl.
Fix:
- Keep the plant in one stable spot once buds form
- Keep the mix evenly moist (not soggy) while in bud
- Avoid drafts and temperature swings
Green segments fading to pale yellow or red
When the green drains to pale yellow or reddish, blame too much direct sun burning the segments, worst in a hot, bright window across the summer. Move it into bright indirect light and screen it from the midday glare. The green fills back in once the light softens.
Fix:
- Move to bright indirect light
- Shade from hot midday summer sun
Toxicity
For all its clawed edges, the Thanksgiving cactus is non-toxic to cats, dogs, horses, and people, a status the ASPCA confirms. Those fibrous, chewy segments hold no poison. The only catch is that eating a lot of them may leave a pet with a brief, mild stomach upset.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Nothing in the flat green segments or the flowers is toxic to cats. A cat that shreds and swallows a lot of the fibrous pads may drool or bring a little back up, then recover on its own.
Dogs None
The chewy stems hold no poison for dogs. A big mouthful of the fibrous segments brings, at worst, a short bout of mild stomach upset.
Horses Safe
The ASPCA lists it safe for horses, and a stray taste of the segments poses no real risk.
Rabbits Safe
Rabbits can nibble near it safely. As with any fibrous green, a large helping of the pads may loosen the stomach for a day.
Livestock Safe
The stems and blooms carry no toxin for grazing animals. A heavy feed on the fibrous segments may bring a short, mild bout of indigestion and nothing worse.
Birds Safe
Pet birds are safe beside this cactus, since none of its green parts are poisonous.
People Safe
Safe for people, children included. The segments are not grown to eat, and their fibrous, stringy flesh would taste unpleasant rather than harm anyone.
Varieties
Schlumbergera shows its range mostly in flower color, across a few closely related forms. The ones below are the most common to see.
'White Christmas'
A truncata cultivar whose blooms open pure white rather than the usual pinks and reds.
'Cambridge'
A truncata cultivar with warm petals that deepen from pink into orange.
Schlumbergera × buckleyi
The true Christmas cactus, a hybrid known by its rounded, scalloped segment edges and a bloom about a month after the Thanksgiving type.
How to propagate
A single flat segment is all it takes to start again, since a broken-off piece roots readily and grows into a whole new chain of stems.
Stem cuttingsEasy
Late spring to early summer (May-June) · Roots in about 3-8 weeks
The best time to root a piece is late spring to early summer, around May or June, while new segments are forming. Twist a chain of 3 to 5 jointed segments free at a joint, let the raw end callus for a day or two, then press it into a moist, well-drained mix and keep the air humid. Pale roots push out in 3 to 8 weeks, and a fresh chain of pads begins.
Myths
A store label reading Christmas cactus means the true species.
Look at the segments and the timing. Most holiday cactus for sale is Schlumbergera truncata, the Thanksgiving or crab cactus, marked by the pointed, claw-like teeth along each segment and a bloom that opens in late fall, about a month before the true Christmas cactus.
The clawed stems of holiday cactus can poison pets.
The ASPCA lists Schlumbergera as non-toxic to cats, dogs, and horses. Those fibrous segments carry no poison, and the most a chewing pet gets is a brief, mild stomach upset after eating a fair amount.