Despite their common names, the Christmas, Thanksgiving, and Easter Cactus all belong to the same genus: Schlumbergera or Rhipsalidopsis (now often reclassified as Hatiora). The Christmas (Schlumbergera × buckleyi) and Thanksgiving (Schlumbergera truncata) cacti are closely related hybrids within the Schlumbergera genus. They are epiphytic cacti, naturally growing on trees in the coastal mountains of southeast Brazil. The Easter Cactus, however, is a distinct species (Hatiora gaertneri, formerly Rhipsalidopsis gaertneri). It is also an epiphyte but hails from the natural forests of Brazil. This shared epiphytic nature means all three prefer more organic, well-draining soil and higher humidity than their desert-dwelling cactus cousins.
The most reliable way to distinguish these plants is by examining their stem segments, called phylloclades, which perform photosynthesis in place of leaves. The Thanksgiving Cactus (S. truncata) has very distinctive, sharply pointed, claw-shaped projections or teeth along the edges of its fleshy green segments. These protrusions resemble a crab's claws, leading to another common name: Crab Cactus. In contrast, the Christmas Cactus (S. × buckleyi) has stem segments with more scalloped or rounded edges; the teeth are far less pronounced and appear as soft, rounded notches. The Easter Cactus (H. gaertneri) has a completely different segment structure. Its edges are almost entirely smooth, with barely visible notches, and small brownish areoles (the spots where flowers and hairs form) dot the margins.
The flowering time and floral morphology are key differentiators, dictated by each plant's unique photoperiodism (response to day length). The Thanksgiving Cactus is the earliest bloomer, producing flowers from late autumn. Its flowers are held horizontally, and the pollen-bearing anthers are yellow. The Christmas Cactus flowers a few weeks later, around mid-winter. Its flowers are more pendulous (drooping) and have purple-brown anthers. The Easter Cactus, as its name implies, flowers in spring. Its floral structure is radically different, featuring vibrant, star-shaped, symmetrical flowers that open with the sunrise and close at dusk. The difference in bloom time is a direct physiological adaptation to their specific pollinators' active seasons in their native habitats.
While all three prefer bright, indirect light and well-draining soil, their needs for triggering blooms differ slightly due to their distinct phenological cycles. Both the Christmas and Thanksgiving Cactus are short-day plants. They require longer periods of uninterrupted darkness (about 12-14 hours) and cooler temperatures to initiate bud formation for their winter blooms. The Easter Cactus, a long-day/short-day plant, requires the opposite for its spring flowering. It needs shorter periods of darkness followed by increasing day length after a winter dormancy period. It also requires a more pronounced cool (around 50°F or 10°C) and dry rest period in winter to set buds successfully, making its dormancy requirements more specific.
