Hands-on, inquiry-based laboratory activities are excellent opportunities to introduce first-year undergraduate students to the lab environment and to catalyze new interest in topics they may not yet know or be as enthusiastic about studying. We describe a multisession introductory laboratory activity that couples the research areas of medicinal drug discovery and plant biology. Selecting from a diversity of native California plants and broadly recognized medicinal plants, students learn and apply an assortment of basic phytochemical assays, analyze preliminary data, and then formulate hypothesis-driven follow-up experiments. Working in small groups, students develop shared project management and collaboration skills, and present activity results to peers in multiple modalities. Furthermore, we summarize findings from 163 student experiments using 29 plant species into an Instructor's Resource Table to facilitate guiding students through their preliminary and follow-up experiments. Lastly, we include student responses from pre- and post-activity surveys on their changing attitudes toward plant biology.