Gardner was born at Rouchel, near Aberdeen in the Hunter Valley, and was educated at Scone Grammar School and the University of Sydney.

He worked as a teacher at Melville, Davis Creek, Ferndale and Stoney Creek schools between 1903 and 1908, when he resigned from the Education Department and returned to farming at his family's property, "Rose Vale".

[11] He unsuccessfully contested Nationalist Party of Australia preselection for the 1919 federal election, again taking on an organiser role.

[15][16][17] In 1922, he was elected to the Australian House of Representatives as the Nationalist member for Robertson, defeating William Fleming, deputy leader of the Country Party.

In parliament, he was a member of the Joint Committee on Public Accounts and was Government Whip and secretary to the United Australia Party caucus.