From my perspective as a Christmas cactus, the most immediate and distressing reason for my buds to fall is a sudden change in my surroundings. I am a creature of habit, especially when I am covered in delicate, pre-formed flower buds. If you recently brought me home from a nursery or moved me from one room to another, the shift in temperature, light, and humidity can be a profound shock. My buds are the most sensitive part of me at this stage. They are programmed to develop under a specific set of conditions. A significant drop in temperature during transport, or a change from the bright, indirect light I was accustomed to, signals to my system that the environment is unstable and potentially threatening. To conserve my energy for survival, I make the difficult decision to abort the buds. Flowering is an energy-intensive process, and I cannot justify it if my basic stability is in question.
My relationship with water is a delicate one. My roots are fine and susceptible to both extremes. If you give me too much water, the soil becomes waterlogged, suffocating my roots and causing them to rot. A root system in distress cannot effectively transport water and nutrients to the rest of my structure, and the buds, being high-maintenance organs, are the first to suffer and drop. Conversely, if you let my soil become bone dry for too long, I enter a state of drought stress. I simply do not have the hydraulic pressure to sustain all my tissues. The buds, which require a constant, gentle supply of moisture, will wither and fall as a survival tactic to redirect what little water remains to my vital stems and leaves. I need soil that is consistently lightly moist, not a cycle of flood and drought.
The very signal that tells me it is time to form buds is light—or rather, the lengthening periods of uninterrupted darkness as autumn arrives. I am a short-day plant, meaning I require long nights (12-14 hours of darkness) and cool temperatures to initiate budding. If, after I have set my buds, my dark period is disrupted, it confuses my internal clock. An errant streetlight, a sudden burst of light from a room you enter, or even frequent flashes from a television can be enough to break the spell. My system interprets this as a false signal, as if the days are getting longer again and the flowering season is over. Consequently, I will shed the buds I no longer believe are seasonally appropriate.
I thrive in the moderate, stable temperatures that mimic my native jungle understory habitat. Drastic temperature fluctuations are a significant source of stress that leads directly to bud drop. A cold draft from a frequently opened door or a window, or the blast of hot, dry air from a heating vent, can be devastating. These conditions cause rapid changes in my metabolic rate and transpiration. The buds cannot adapt quickly enough to such violent swings. Similarly, placing me too close to a heat source or a freezing windowpane creates a microclimate that is entirely unsuitable for the delicate process of flowering. The stress hormone ethylene, which can trigger bud and flower drop, is often produced in higher amounts under these stressful temperature conditions.
Please understand that my buds are attached by a very fragile connection. Once I am in a spot where I am happy and budding, even minor physical disturbances can cause them to detach. If you frequently rotate my pot, bump into me while passing, or if I am in a high-traffic area where vibrations from slamming doors or loud noises are common, the physical jostling can literally shake my buds loose. It is a mechanical failure. The abscission layer at the base of the bud, which is designed to eventually allow a spent flower to fall, is prematurely activated by this constant physical agitation. For me, a stable and quiet location is not a luxury; it is a necessity for successful blooming.
