Butea superba is a vining shrub native to Vietnam, Thailand, and India. It is sold as a oral supplement, and some evidence exists that it increases the male hormone Dihydrotestosterone (DHT). This could indicate supplementation could have positive effects on beard growth.

Whilst it should be noted that the evidence for DHT boosting is scarce, and albeit weak, it is undoubtedly interesting.

A case study1) of a 35 year old male patient was recorded with extremely high androgen levels. The case study suggested that his extremely high levels of DHT were due to his ingestion of butea superba. It was also noted that free testosterone was elevated. Upon ceasing consumption of the herb, the patients DHT levels turned to normal. The correlation between his high androgen levels and subsequent decrease when ceasing his butea superba supplementation, would suggest that the herb was responsible for his elevated DHT levels. The dose in the case study was not reported.

Given DHT's relationship with beard growth, supplementing with butea superba, may improve the linear growth of facial hair2).

Hyperandrogenemia due to ingestion of Butea superba|http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3354878/
Relationship between plasma testosterone and dihydrotestosterone concentrations and male facial hair growth|https://www.ncbi.nlm.nih.gov/pubmed/7126460