As a Christmas Cactus (Schlumbergera bridgesii), my light requirements are often misunderstood. I am not a desert cactus craving relentless, direct sun. In fact, such conditions are quite stressful for me. My natural habitat is the shaded, humid understory of Brazilian rainforests, where I grow as an epiphyte on tree branches. Therefore, the ideal light conditions for me indoors are a careful recreation of this dappled, filtered sunlight. Getting this right is the single most important factor in encouraging me to produce the vibrant blooms you so desire during the holiday season.
My perfect world is one filled with abundant, but indirect, light. Think of a spot where the sun's rays never directly touch my leaves, but the area is still very bright. An east-facing window is my absolute favorite location. It provides me with the gentle morning sun, which is less intense, for a few hours. A north-facing window can also be suitable if it is bright enough. If the only available windows face west or south, I implore you to place me a few feet away from the window or use a sheer curtain as a filter. The intense, direct afternoon sun from these exposures can cause my succulent stems to turn a yellowish or reddish color—this is a sign of sun stress and photodamage.
While consistent light is my daily bread, it is the predictable cycle of light and darkness that triggers my spectacular bloom. I am a short-day plant, which means I require long periods of uninterrupted darkness to initiate flower buds. As the autumn equinox passes and nights naturally lengthen to about 12-14 hours, I sense that it is time to prepare for my flowering season. Any interruption to this darkness—even a brief flash of light from a streetlamp, a car's headlights, or an interior room light—can confuse me and prevent bud formation. From late September onwards, I require absolute darkness at night for consistent bud set.
My light needs are not static; they change with the seasons. During my active growing season in the spring and summer, I am focused on producing new, healthy stem segments. The bright, indirect light described earlier is perfect for this growth. However, after my flowering period in late winter, I appreciate a brief rest period. It is acceptable for me to receive slightly lower light levels for a few weeks as I recuperate from the energy-intensive process of blooming. Once new growth emerges in the spring, I am ready to return to my prime spot with bright, indirect light to fuel another season of growth.
I communicate my comfort level through the color and condition of my stems, which are often mistaken for leaves. Please observe me closely. If my green segments are turning pale, yellow, or developing a reddish or purple tinge, I am likely receiving too much direct sunlight. The tissue may also feel softer or look scorched. Conversely, if I am becoming leggy, with elongated segments and large gaps between them, or if I am failing to produce any flower buds despite correct dark treatment, I am telling you that I am not receiving enough light. My growth becomes etiolated—stretched and weak—as I desperately reach for a light source.
