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.
Marathon County, Wisconsin. Marathon County is a county located in the U.S. state of Wisconsin. As of the 2010 census, the population was 134,063. Its county seat is Wausau. It was founded in 1850, created from a portion of Portage County. At that time the county stretched to the northern border with the upper Michigan peninsula.