If you are growing your Gardenia as a potted plant indoors, keep it out of direct, hot sun, and allow it to only get bright light. I think that your 'black mold' is more than likely an algae growth, which is a cosmetic problem for your plant rather than a health problem.
Monona is a city in Dane County, Wisconsin, United States. The population was 7,533 at the 2010 census. It is completely surrounded by Madison and is part of the Madison Metropolitan Statistical Area.
Birnamwood is a village in Marathon and Shawano Counties in the U.S. state of Wisconsin. It is part of the Wausau, Wisconsin Metropolitan Statistical Area. The population was 795 at the 2000 census. The village is located mostly within the Town of Birnamwood in Shawano County; only a small portion extends into the Town of Norrie in adjacent Marathon County. Until the 1990s, Birnamwood was home to the world's largest fiberglass badger.