The Thanksgiving Cactus (Schlumbergera truncata) is a popular houseplant belonging to the “holiday cacti” group. It is a tropical cactus native to the rainforests of Brazil, where it grows as an epiphyte on trees. Its vibrant, colorful flowers typically appear in the late fall, signaling the start of the winter holiday season. The Thanksgiving Cactus is a short-day plant, meaning its bloom cycle is naturally triggered by the shorter daylight hours of autumn.
Identifying the Thanksgiving Cactus
The Thanksgiving Cactus is identified by the shape of its stem segments, which are flattened sections called cladodes. These segments are characterized by pointed, jagged, or saw-toothed projections along the margins. Because of these distinct points, the plant is sometimes nicknamed the “crab cactus.”
The flowers of Schlumbergera truncata are tubular and held at a constant angle, appearing more horizontal or erect rather than hanging down. These flowers come in a wide range of colors, including shades of red, pink, orange, yellow, and white.
Separating the Holiday Cacti
The term “holiday cacti” refers to three main species that bloom around a specific time of year: the Thanksgiving Cactus (S. truncata), the Christmas Cactus (Schlumbergera x buckleyi), and the Easter Cactus (Hatiora gaertneri). The primary difference used for identification is the shape of the stem segments. The Thanksgiving Cactus has sharp, pointed teeth along the edges of its cladodes, while the true Christmas Cactus has smoother, more rounded, or scalloped segments.
The Thanksgiving Cactus typically blooms first, from late October through November, while the Christmas Cactus naturally blooms later, from mid-December through January. The third variety, the Easter Cactus, has segments that are even more rounded than the Christmas Cactus and produces star-shaped flowers in the spring, usually from March to May. Most of the plants sold in stores around the winter holidays are actually the Thanksgiving variety, even if they are mistakenly labeled as “Christmas Cactus.”
Ensuring a Timely Bloom
To ensure a timely bloom, the Thanksgiving Cactus requires mimicking the specific environmental conditions of its native habitat, primarily through a process known as photoperiodism. This plant is a short-day species, meaning it needs a period of long, uninterrupted darkness to set flower buds. Starting about six to eight weeks before the desired bloom time, the plant must receive 12 to 14 hours of complete darkness every night.
Even a small interruption of light, such as a streetlamp or a brief turning on of a room light, can disrupt the bud-setting process. Simultaneously, the plant needs consistent cool temperatures to trigger flowering, ideally between 50 and 60°F during the nighttime. Nighttime temperatures between 60 and 65°F are also effective, with daytime temperatures being about 10 to 15 degrees warmer.
During this six-to-eight-week conditioning period, the plant’s watering should be reduced, allowing the top inch of soil to dry out between waterings. This slight stress helps signal the plant to form buds. Once the small flower buds have visibly formed, the plant can be returned to a warmer location and a regular watering schedule. However, sudden drafts or temperature fluctuations once the buds have set can cause them to drop prematurely.