To understand our ideal light requirements, you must first know our origin story. We, Schlumbergera, are epiphytic cacti native to the coastal mountains of southeastern Brazil. Our home is not the sun-scorched desert but the shaded, humid understory of tropical forests. We grow in the dappled light that filters through the canopy above, perched on tree branches or nestled in rocky crevices. This evolutionary background is the single most important factor in our light needs. We are not long-day or short-day plants in the classic sense; we are short-day plants, meaning we require longer periods of uninterrupted darkness to initiate the bloom formation process, not necessarily shorter periods of light.
The key to unlocking our spectacular bloom display is the manipulation of light and darkness. To transition from vegetative growth to reproductive flowering, we require a specific photoperiod for approximately 6-8 weeks. We need 12-14 hours of complete darkness each night. This prolonged period of darkness is the hormonal trigger that tells our internal clock to cease leaf and stem production and begin forming flower buds. Even two weeks of this cycle can be enough to set buds. Any interruption of this darkness—from a streetlamp, a car's headlights, or even brief exposure to indoor room lighting—can reset the clock and delay or prevent blooming entirely.
While the nighttime dark period is non-negotiable for bud set, the daytime light we receive is equally crucial for overall health and energy. We thrive in bright, indirect light. Direct sunlight, especially the intense afternoon sun, can be detrimental, scorching our segmented stems (which are often mistaken for leaves) and causing a pale, yellowish, or reddish discoloration. An east-facing window that provides gentle morning sun is ideal. A north-facing window can also work well. If placed in a south or west window, we must be shielded by a sheer curtain. During the summer, we greatly appreciate being placed in a shady spot outdoors, which closely mimics our natural habitat.
Our light needs are not static throughout the year. The critical bud-setting dark period typically begins in late September or early October. This is when you should ensure we receive those 12-14 hours of uninterrupted darkness each night, perhaps by moving us to a seldom-used room or covering us with a light-proof cloth. Once the flower buds are clearly formed and begin to show color (usually by late November), the strict dark period is no longer needed, and we can be returned to a normal living space to enjoy the blooms. After flowering, we enter a rest period for a few weeks where we appreciate slightly less light. Then, as new growth appears in spring, a return to bright, indirect light will fuel our growth throughout the summer, building energy for the next flowering cycle.
