To extract all beneficial properties from coarse leaves, stems, roots, and barks, a decoction is the preferred method.  To make a decoction use the recommended amount herbs and water in safe cookware and simmer them, uncovered, until the volume of the water is decreased by half.

Sometimes an herbalist will recommend that the decoction is covered to prevent the escape of volatile oils from plants like valerian, cinnamon, burdock, or willow during the simmering process.