Vaccaria is a monotypic genus of flowering plants in the family Caryophyllaceae containing the single species Vaccaria hispanica. It is known by several common names including cowherb, cowcockle, cow basil, cow soapwort, and prairie carnation. Its subspecies were previously treated as separate species.
It is an annual herb with blue-gray, waxy herbage and pale pink flowers.
It is native to Eurasia but can be found in many other regions as an introduced species and a common weed.
The seeds of Vaccaria are used in Chinese medicine. This medicinal is known as wáng bù liú xíng (王不留行, so beneficial at promoting circulation, even the "king cannot stay its movement"). It is used to regulate specific types of menstrual concerns, ameliorate certain types of arthritis, promote lactation, promote blood circulation, and relieve some types of swellings.