Outdoor, hands-on and experiential learning, as opposed to instruction-based learning in classroom, increases student satisfaction and motivation leading to a deeper understanding of the subject. However, the use of outdoor exercises in undergraduate biology courses is declining due to a variety of constraints. Thus, the goal of this paper is to describe a convenient, no-cost and flexible exercise using an on-campus botanical tour for strengthening specific knowledge areas of major plant groups. Its assessment on conduct and coverage, and student-perceived and actual knowledge gain is also described. Data presented derived from traditional biology undergraduates in sophomore year over nine fall and three spring semesters. Conduct and coverage was assessed using a summative survey including open-ended questions administered to 198 students. A pre- and post-exercise survey addressing 10 knowledge categories was administered to 139 students to evaluate student-perceived knowledge gain. Quiz grades from the on-campus tour exercise were compared with average quiz grades from two in-class plant-related labs of 234 students to assess actual knowledge gain. Each student reporting on the conduct and coverage indicated either one or a combination of outcomes of the exercise as positive engagement, experiential learning, or of interest. Student-perceived improvement was evident in all ten knowledge categories with a greater improvement in categories learned anew during exercise compared to subjects reviewed. Quiz grades from the exercise were >11% greater than quiz grades from the two in-class plant-related labs. Active learning with interest likely contributed to the increased perceived and actual knowledge gains. Suggestions for adoption of the exercise in different settings are presented based on both student comments and instructor's experience.