From my perspective as a Dendrobium orchid, my primary purpose is to survive and reproduce. Flowering is my grand, energy-intensive strategy for reproduction. When I withhold my blooms, it is not out of spite, but because my fundamental needs are not being met to support such a demanding biological process. Here are the reasons from my point of view.
I am a light-hungry organism. My leaves are sophisticated solar panels designed to manufacture the massive amounts of carbohydrates (sugars) required to form flower buds. If the light is too dim, I simply cannot produce enough energy to support anything beyond basic leaf and root growth. I will remain in a perpetual vegetative state. Conversely, if the light is too harsh and direct, my leaves will scorch, turning a pale yellow or brown. This damages my food-production factories, weakening me and making flowering impossible. I need bright, indirect light, like that filtered through a tree canopy. A tell-tale sign I am happy is leaves that are a light to medium green, not dark green (too little light) or yellowish (too much).
Many of my type, particularly the deciduous Dendrobium nobile and its relatives, require a distinct winter rest. As temperatures drop and daylight shortens in my native habitat, I receive a clear signal to slow down. During this period, you must significantly reduce watering and stop fertilizing me entirely. This cool, dry rest is not neglect; it is a crucial environmental trigger. Without this period of stress, I become confused. I continue to grow vegetatively and will not initiate flower bud development. I need several weeks of nights cooler than 55°F (13°C) and very little water to tell me it's time to shift my energy from growth to blooming.
Feeding me is appreciated, but the type of food matters greatly. A fertilizer high in nitrogen (the first number on the package) will promote lush, green leaf growth at the expense of flowers. You are essentially telling me to keep growing leaves, not blooms. To encourage flowering, I need a fertilizer blend higher in phosphorus (the middle number), such as a 10-30-20 formula, during the active growing season leading up to my bloom time. However, please remember to cease all feeding during my crucial dormancy period mentioned above.
I thrive on a natural temperature fluctuation. While I enjoy warmth during the day for photosynthesis, a drop in temperature at night, especially in the autumn, is another critical signal for me. This differential between day and night temperatures (a 10-15°F / 5-8°C drop is ideal) mimics my natural mountainous or highland habitat and tells my internal chemistry that the season is changing and it is time to prepare for reproduction. If I am kept in a consistently warm environment with little variation, I lack the cue to begin the flowering process.
There is a delicate balance. Being severely root-bound in a tiny pot can cause enough stress to sometimes trigger flowering as a last effort to reproduce. However, being excessively comfortable in an overly large pot can also be a problem. My roots may focus on colonizing the vast space of damp potting mix rather than sending energy upwards for blooms. Furthermore, a pot that is too large holds moisture for too long, risking root rot, which will severely weaken me and prevent flowering. A snug pot is generally best for my kind.
