Black root (Veronicastrum virginicum), also known as Culver’s root, has been traditionally used in North American herbal medicine, particularly by Native American and early European settlers. The plant was employed as a purgative and for various digestive complaints, but some records indicate its use for "female complaints," which may have included menstrual irregularities. However, these traditional uses are not well documented or specific, and there is little detailed ethnobotanical evidence linking black root directly to the treatment of menstrual irregularity as a primary indication.

Scientifically, there are no clinical trials or pharmacological studies that validate the efficacy or safety of black root for menstrual irregularities. Modern herbal literature rarely lists black root as a remedy for menstrual issues, and its use in this context is largely historical rather than evidence-based. The available traditional evidence is weak and mostly anecdotal, lacking clear dosage, preparation, or mechanism of action. Furthermore, black root contains potentially toxic compounds and is considered by some sources to be unsafe for internal use without expert guidance.

In summary, the use of black root for menstrual irregularity is based on limited and nonspecific traditional references, with no scientific validation to support its efficacy or safety for this purpose.