Gardner grew up in Port Hope, Ontario, Canada. She is the daughter of an Anglican minister and school principal. Gardner earned a degree in journalism from Ryerson University. She began her career on Canadian Broadcasting Corporation (CBC) radio in 1990. She worked on the program "As It Happens" at first. Gardner worked for more than a decade as a producer, reporter and documentary-maker for CBC Radio current-affairs. She also worked for Newsworld International. Her time at Newsworld dealt mainly with pop culture and social issues.