Disclosure: Amazon links on this page are affiliate links, so this site may earn a commission at no extra cost to you. Commissions don’t decide which products are recommended. See the full affiliate disclosure.
Thanksgiving cactus (Schlumbergera truncata) sets flower buds after several weeks of long, uninterrupted nights and cool temperatures in fall, according to Clemson HGIC and UMN Extension. Iowa State Extension recommends bright, indirect light and warns that sudden changes can make the plant drop its buds.
What a Thanksgiving cactus is
Schlumbergera truncata (Haw.) Moran is an accepted species in the cactus family, native to Brazil Southeast, per Kew POWO. POWO describes it as "a succulent epiphyte" that "grows primarily in the wet tropical biome." Older names include Epiphyllum truncatum and Zygocactus truncatus, which Iowa State Extension also lists and calls the species "the most familiar holiday cactus."
The plant has no true leaves. The flat green pieces are stem segments; NC State Extension calls them cladodes, "flattened, green internodes that function like leaves," each about 1.5 to 2.25 inches long. NC State lists crab cactus, claw cactus, lobster cactus, holiday cactus and false Christmas cactus among its common names.
How to recognize it
Look at the edges of the stem segments. Clemson HGIC says each segment of a Thanksgiving cactus has "2 to 4 saw-toothed serrations or projections along the margins," while Christmas cactus margins are "more rounded." Clemson adds that Thanksgiving cactus anthers are yellow and Christmas cactus anthers are purplish-brown. NC State describes Thanksgiving cactus flowers as "erect, tubular, and do not hang down like the flowers on Schlumbergera x buckleyi." Iowa State gives flower colors from white to red, lavender and salmon-orange.
For a side-by-side table that includes the Easter cactus, see Christmas cactus vs. Thanksgiving cactus.
How to get it to bloom
UMN Extension calls holiday cacti "short-day" plants that also need cool nights. The extension sources agree on those two triggers but give different figures, so each is listed as published.
- Long, uninterrupted nights. Clemson HGIC says "Fourteen hours or more of continuous darkness each day is required" for bud set. Iowa State says most need 14 to 16 hours of uninterrupted darkness, though some cultivars bloom with as little as 12. UMN Extension says that at night temperatures of 60 to 65°F, plants "must have at least 12 hours of complete darkness every night for about 6 weeks to bloom," with bright light for the rest of each day.
- Cool nights. UMN Extension says plants given night temperatures of 55°F "will bloom in approximately 5 to 6 weeks" and are unlikely to bloom with nights above 65°F. Iowa State says temperatures above 70°F prevent flowering even with short days, and that some plants bloom at 55°F in fall regardless of day length. Clemson says night temperatures of 50 to 59°F set buds regardless of day length, but that "bud drop may occur at 50 ºF."
- No light at night. Clemson warns that "as little as 2 hours of interrupted lighting will inhibit flower bud set" and that street lights, car lights or indoor lighting can disrupt the dark period. Iowa State names lamps and kitchen lights.
Starting late (mid-October)
Clemson recommends starting long nights "about the middle of September" and keeping them up for at least 6 weeks; buds "normally will be visible in 3 to 4 weeks." UMN Extension says Thanksgiving cacti bloom "after approximately 6 weeks of short days." A plant that starts long nights and cool nights in mid-October is about a month behind Clemson's schedule; six weeks from mid-October is late November. Iowa State gives a typical bloom window of mid-November to late December, so a late-November bloom still falls within that window.
If buds are already showing, the light schedule no longer matters: Clemson says "The photoperiod has no effect on flowering once the buds are set." From that point, keep the mix evenly moist, as Clemson advises, and leave the plant where it is until the flowers begin to open, as Iowa State advises (see bud drop, below).
Light
Iowa State says holiday cacti indoors prefer bright, indirect light. Clemson says they grow best in light shade, that full sun helps in fall and winter, and that bright summer sun can make plants "look pale and yellow." UMN Extension recommends part shade (3 to 6 hours of sun a day) for plants kept outdoors in summer and warns that excessive sunlight may cause "pale green branches, drought and sunburn." NC State notes that direct sunlight can scorch the stems.
Watering
This is a forest cactus, not a desert one. Iowa State says "Unlike desert cacti, holiday cacti shouldn't stay dry," and that the soil should be kept evenly moist while the plant is budding and flowering; it also says overwatering leads to limp growth and root rot. Clemson says to water "when it is dry to the touch," to keep the mix evenly moist after buds set in fall, and never to let water stand in the saucer. UMN Extension also says to let the soil dry between waterings and not to leave plants sitting in excess water.
NC State mentions the plant's "high humidity requirements" and notes that bathrooms are a popular spot for it.
Soil and repotting
The mix has to drain. Clemson says it "must be well-drained with good aeration" because these are epiphytic cacti. UMN Extension suggests 1 part sterile potting soil, 2 parts peat moss and 1 part sharp sand or perlite. Iowa State says well-drained potting soil works and a special cactus mix is not required, while NC State suggests a well-drained cactus or succulent potting mix.
Repot rarely. Clemson says holiday cacti flower best "somewhat pot bound" and need repotting only about once every three years, in spring. Iowa State says to repot only when the plant has completely outgrown its container.
Temperature
Clemson gives 70 to 80°F during the April to September growing season, says not to leave plants outside if temperatures will drop below 50°F, and says not to let temperatures rise above 90°F once buds are set. NC State also gives 70 to 80°F. For indoor plants, UMN Extension recommends days of 65 to 70°F and nights of 55 to 65°F, and Iowa State gives 60 to 70°F.
Fertilizer
The sources set different calendars:
- Clemson: monthly with a half-strength soluble fertilizer from when new growth starts in late winter or early spring, stopping in late summer "for greater flower bud production in the fall." Clemson also suggests Epsom salts at 1 teaspoon per gallon of water during the growing season.
- UMN Extension: monthly from June through August with a balanced houseplant fertilizer at half strength, then a low-nitrogen, high-phosphorus and potassium formula such as 0-15-10 in fall.
- Iowa State: monthly during the growing season.
Care after blooming
Iowa State says to move the plant to a cooler spot and water less often after flowering. UMN Extension says to water less until growth picks up again in spring or early summer, and to prune after flowering by cutting where two stem sections join to encourage branching. Clemson suggests pinching stems back in early June for more branch tips, then "leveling" at the end of September to remove tip segments less than 1 cm long. NC State says a plant may bloom a second time "as the days lengthen in February."
Bud drop and other problems
| Problem | Causes named by the source | What the source advises |
|---|---|---|
| Buds drop before opening | Too many buds, or a sudden change in temperature, light or other conditions, including a dried-out mix (Clemson); drafts or sudden changes in temperature or humidity (UMN); too few dark hours (NC State) | Don't move the plant until flowers begin to open (Iowa State); if it must go to a warmer room, move it as soon as buds appear (UMN); keep the mix evenly moist after bud set (Clemson) |
| No flowers | Light interrupting the long night (Clemson); nights too warm, or low nutrients (UMN) | Total darkness for at least 12 hours a night and bright light the rest of the day; cooler nights (UMN) |
| Root rot | The major disease, which can be prevented by avoiding excessive watering (Clemson) | Avoid overwatering; see the root rot guide |
| Pale or yellowish stems | Bright summer sun (Clemson) | Light shade in summer |
| Gray, fuzzy growth | Gray mold in high humidity with poor air circulation (NC State) | Improve air movement |
| Insects | Mealybugs, soft brown scale, red spider mites, aphids and fungus gnats (Clemson) | See the guides to mealybugs, scale, spider mites, aphids and fungus gnats |
Propagation from stem segments
Clemson says cuttings are taken in May or June. Its method: pinch off sections with 3 to 5 stem segments, let the cut ends callus in outdoor shade for a day or two, pot them, and keep them in bright, indirect light until roots form "in three to eight weeks."
Iowa State uses 2 to 5 segments removed at a joint, callused overnight and set about 1 inch deep in moist perlite or coarse sand; it says "Roots form in 6 to 8 weeks." NC State uses two or three segments left to callus for a few days. UMN Extension notes these plants "can live over 100 years, and are often passed down from generation to generation."
Is Thanksgiving cactus toxic to cats and dogs?
The ASPCA's Toxic and Non-Toxic Plants database has no entry under Thanksgiving Cactus, Easter Cactus, Crab Cactus, Claw Cactus or Holiday Cactus. Its Christmas Cactus entry gives the scientific name Schlumbergera bridgesii, lists Easter Cactus as an additional common name, and classifies the plant as non-toxic to dogs, cats and horses. That entry does not name S. truncata. Iowa State lists S. bridgesii as an older name for the Christmas cactus, and Kew POWO treats it as a synonym of S. russelliana, one parent of the Christmas cactus hybrid. The ASPCA's separate Shrimp Cactus entry names Schlumbergera russelliana and also lists it as non-toxic to dogs, cats and horses.
For S. truncata itself, NC State's Plant Toolbox page tags the species "non-toxic for cats" and "non-toxic for dogs," but gives no poison severity rating.
Non-toxic is not a promise that eating it causes no harm. The ASPCA's plant list notes that "the consumption of any plant material may cause vomiting and gastrointestinal upset for dogs and cats." If a pet ate part of the plant and you are worried, call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435. For other options, see plants safe for cats.
Frequently asked
Sources: Kew POWO — Schlumbergera truncata, Kew POWO — Schlumbergera bridgesii, Clemson HGIC — Thanksgiving & Christmas Cacti, Iowa State Extension — All About Holiday Cacti, UMN Extension — Holiday cacti, NC State Extension — Schlumbergera truncata, ASPCA — Christmas Cactus, ASPCA — Toxic and Non-Toxic Plants, ASPCA Animal Poison Control, ASPCA: Shrimp Cactus