Romeo and Juliet - At the beginning of Scene 3, why does Friar Lawrence spend so much time discussing his passion for herbs and alchemy?

At the beginning of scene 3 in the classic Romeo and Juliet, Friar Lawrence takes so much time sharing and discussing his passion for herbs and alchemy because herbs are good for the health due to the nourishment it gives. He believes that like herbs with two elements, men can also be good or evil.