Answer: I think transplant shock is causing the problems you describe, but there are so many variables - temperature, sunlight, over-fertilization, etc. Over-exposure to sunlight might cause the leaves to yellow and fall off. As beautiful as they are, gardenias can be a real challenge to grow - as you know. They're very picky about their surroundings. They need at least a half day of full sun to bloom, but at the same time, the hot afternoon sun can be tough on them. Morning sun is best, so an eastern location is ideal. Leaf drop can also be caused by improper soil pH (gardenia require 5 to 5.5pH - on the acid side.) Yellowing and leaf drop are also signs of various soil nutrient deficiencies such as nitrogen, zinc, and iron. I think you've addressed these problems with fertilizer - although I'm concerned that you're using 6 spikes for a single plant. Over-fertilization can burn the roots of your plant and cause the foliage to suddenly turn yellow and drop. I'd remove 4-5 of the stakes (depending upon the size of your plant). A single fertilizer stake should provide all the nutrition your gardenia needs. Finally, if the air is too dry, your plant will drop buds and leaves. Try sprinkling the plant every morning to increase humidity (and also discourage spider mites!). Hope these suggestions help!
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