Romeo and Juliet - At the beginning of Act 2, Scene 3, why does Friar Lawrence spend so much time discussing his passion for herbs and alchemy?

Friar Lawrence spent time discussing about his passion for herbs and alchemy because these are important elements in the final act. He explains that there is a flower which if you smell, you will feel better but if you eat the fruit, you will fall into coma. These are foreshadowing for the final act.