Answer: Gardenias can be tricky. Since it is forming buds, you must be doing almost everything right. Based on your description it may be a case of the air being a little too dry or perhaps a temperature issue, but as long as they are not falling off it may just mean you still need to be patient a little longer.
Do not make any drastic changes as this will definitely cause the buds to drop. You could try setting it in a pebble tray. Fill a shallow tray with pebbles, add water to just below the top of the pebbles. Set the container on the pebbles, make sure it is above the water and not sitting in the water. Keep the water topped up as it evaporates. Also, here are some general care tips for gardenia, maybe you will see something helpful there. Good luck!
Gardenias are finicky, and any change of location or humidity or sun can set them back, so do not be too surprised if it suffers some initial shock from being moved.
In general, bright light is essential, but avoid direct mid-day sun in the summer. It may summer outside when temperatures are settled, place it in a bright location out of direct sun, in dappled light all day or in gentle morning sun. Buds that turn black and drop, and bottom leaves that are yellowed are sure signs that gardenias aren't getting enough light.
For flower buds to form and thrive, night temperatures need to be between 60-65F. During the day, temperatures should be 70-75F. A very constant, even temperature within these ranges is required or buds will drop. Also avoid drafts or moving the plant. Simply moving the plant often causes bud drop, as may any imbalance in the growing conditions.
Keep the soil evenly moist (but not sopping wet)at all times except in winter when watering should be reduced slightly to compensate for the seasonally slower growth.
Fertilize regularly but lightly during active growth periods (spring and summer) with a water soluble fertilizer for acid loving plants according to the label instructions. Check the label also to make sure it includes micronutrients or "minors" to assure a broad based supply of minerals.
Gardenias are very susceptible to spider mites, which can distort the buds and cause leaves to yellow and drop. Look on the undersides of the leaves for tiny black specks and whitish webbing. If necessary, use an insecticidal soap spray according to the label instructions to control these, be sure to repeat to control subsequent generations and treat all surfaces of the plant. Washing the plant with a spray of tepid water can also help rinse them away.
Routine misting with water helps raise the humidity and consequently discourages spider mites but it is better to set it on a humidity tray of pebbles and water or use a humidifier especially during the winter heating season when indoor air is very dry.
Finally, yellow leaves can be a natural occurance since the old leaves normally turn yellow and fall off, or could indicate inadequate light, or can signal insufficient water or even the use of hard water. Leaf drop can also be caused by improper soil pH (gardenias require 5 to 5.5 pH - on the acid side) or a nutrient deficiciency.
As you can see, these are not easy plants. Occasionally we get lucky and a gardenia will thrive. If not, don't take it personally, they are very difficult.
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