Gardenias can be temperamental. Bud drop (and leaf drop) can be an irritating problem. Bud drop is when flower buds abort right before blooming. Common causes include low humidity, overwatering, underwatering, insufficeint light, high temperatures, temperature fluctuations, cold drafts or a change in plant locations. I suspect your problem is low humidity, especially at this time of year. Try placing your plant on top of a water-tight tray filled with pebbles and filled with water to help maintain a higher level of humidity for your gardenia. Good luck!