Q.A gardinia just put into ground
Just a put a new gardinia plant next to an existing gardinia plant (which is doing well for 2 years), new plant lost most of its leaves, has small buds that bloomed very small flower, is something wrong with soil?
Your plant is likely shocked from the location change and planting.
Gardenia are very finicky and do not adjust quickly to transplant.
Make sure your are watering the newly planted Gardenia and that the soil is moist but well draining.
Here is a link to refresh you on the care requirements.