This ingredient is used to thicken gumbo at the very end of the cooking process, as it should not be allowed to boil or it will cause liquids to become stringy. Filé Powder is made from ground sassafras leaves. The sassafras tree, sassafras albidum is native to the Gulf Coast region of the United States and it may grow up to 20 or 30 feet tall with distinctive leaves that take on three different mitten-like shapes. A tea is sometimes brewed from the roots and the bark and roots were long used to flavour root beer. The Choctaw Indians were using Filé Powder when the Cajuns arrived in Louisiana from Acadia in the 1600s and the Cajuns learned these techniques from them.