Gumbo file powder is a spice made from the powdered leaves of the sassafras tree. An important ingredient in Cajun cooking, it's commonly used in gumbo both for its flavor and its thickening properties.
The aroma of file powder is reminiscent of eucalyptus or Juicy Fruit gum. File powder has a long history; before it became an integral part of Cajun and Creole cooking, the Choctaw added pounded sassafras leaves to their soups and stews. Consumers can find file powder in the spice aisle of local grocery stores or speciality spice shops. Cooks stir the powder into foods after removing them from the heat for best flavor.