Herb-Very decorative perennial flowering groundcover plant grows up to 15 cm high. Purple, pink and white flowers collected in cylindrical inflorescences. Blooms in the second year from mid-June to mid-August. Use for borders and stony hills. Prunella vulgaris plant is commonly known as the self-heal herb. It has been used medicinally for centuries. In fact, the entire plant, which is edible, can be used both internally and externally to treat a number of health complaints and wounds. The plant’s most common use is for the treatment of cold sores.