Marshmallow Herb & Root - Althaea officinalis. The leaves, flowers and the root of A. officinalis all have medicinal properties. The leaves, which are collected in summer as the plant begins to flower, have demulcent, expectorant, diuretic, and emollient properties. It is generally used in ailments of the lungs and the urinary systems, specifically in urethritis and kidney stones. The root, which is harvested in late autumn, has demulcent, diuretic, emollient, and vulnerary properties. It is generally used for digestive and skin problems, specifically inflammations of the mouth