Your Double Mint Gardenia can be planted in the ground in early fall. When you do, be certain to pack in the dirt around the roots, mulch the top, and water well. You will want to plant it early enough in the fall when the ground is still warm so the roots can grow a little and get settled in. During the winter, be certain to water it periodically. While it is still in the container in your garden, a place with part shade is better than full sun. The afternoon sun might be too much. Have it in a container that has good drainage and plan to water daily. Fertilize spring, summer, and fall with a product for acid-loving plants such as azaleas and hydrangeas. There are many good products on the market. When flowers start to brown, just snip them off with pruners or gardening scissors.
Thanks for writing!