Mushrooms are not harmful to an herb garden. They will sprout up when there is decaying undergrowth such as past vegetation. Most of the mushrooms that show up in your garden are not the edible kind, but they will help break down the larger nutrients in the soil.
About this Author
Melody Dawn has been writing since 2004. Her work has appeared in the "Gainesville Times," "Player's Press" and USA Today. Her writing focuses on gardening, home improvement, travel, sports, business, parenting and education. Dawn holds a Master of Business and is working on a Master of Journalism.