Xia Ku Cao, Prunella (Prunella Vulgaris) is a perennial, 10-40 cm high with creeping rhizome. The stem is tetrahedral, ascending, and sometimes reddish in color. Leaves are without stipules, opposite, simple. The upper leaves are sessile, serrated. The flowers are small, bisexual, purple-blue or blue. The fruit breaks up into four erems when ripe. Prunella Vulgaris blooms from June to September.