A fragrance diffuser and method of adjusting the evaporation rate of fragrance from a diffuser includes a container having an opening communicating with the interior of the container. A quantity of granular solids material such as silica sand, calcium carbonate sand, salt or starch is located in the container, and a fragrance material is mixed with the solids material to form a solids material-fragrance material mixture that is free of solvents, or includes a minor amount of a low volatility solvent. Wicking material is inserted through the opening of the container, and a portion of the wicking material is immersed into and supported by the solids material-fragrance material mixture. The fragrance material migrates along or through the wicking material and evaporates into the surrounding environment. The evaporation rate of fragrance from the diffuser can be adjusted by varying the length of the wicking material immersed into the granular solids material-fragrance mixture.