Preheat dehydrator between 90°F and 115°F (32-46°C); spread rose petals or buds equally on dehydrator trays lined with sheets. Dehydrate for 4 to 12 hours or more if humid. Rose petals will shrink to half their sizes when totally dry.
Measure powdered orris root in a large glass bowl. Pour measured essential oil over powder; Pour in dried flower petals and stir well.
Package in a container and store. Potpourri stays fragrant for 3 months if in an open bowl and 6 months if packaged in a tightly closed container. Use a vacuum sealer for best storage.
