 The four main species of "Boswellia", "B. sacra" (synonyms "B. carteri" and "B. bhaw-dajiana"), "B. frereana", "B. papyrifera", and "B. serrata", produce true frankincense, and each type of resin is available in various grades.The grades depend on the time of harvesting, and the resin is hand sorted for quality.