St. Andrew, St. John, St. Peter, Aaron? Why are so many Hypericum named for religious figures? Well, first of all we are speaking English in the Western world. If we were in India or China, names would be different. And of course Christianity pervades the culture of the time when English was becoming a language. So it was logical to name a plant that blooms around St. John's Feast Day (June 24) after John. Then we hoped that the plant was bestowed with powers to calm and heal. And we still do. You can get a bottle of extract for $3.96 from Walmart. The other religious names seem to flow from St. John's plants. In particular, four-petaled species with their cross pattern cried out for Christian references. Those species were also used medicinally, but had a milder effect and have pretty much fallen out of the herbal trade. Then there's Hypericum hypericoides.
A St. John's-wort like a St. John's-wort? That name happened because the four-petaled species used to be genus Ascyron. When they were lumped into Hypericum, they got to keep their former specific names. St. Andrew's cross grows in AL, AR, DE, FL, GA, IL, IN, KS, KY, LA, MA, MD, MO, MS, NC, NJ, NY, OH, OK, PA, SC, TN, TX, VA, and WV. Martin Co FL, 1/27/13. St. John's-wort family, Hypericaceae.