Designers often borrow from the natural world to achieve pleasing, unobtrusive designs. We have extended this practice by combining living plants with sensors and lights in an interactive display, and by creating a robotic analogue that mimics phototropic behavior. In this paper, we document our design process and report the results of a 2-week field study. We put our living plant display, and its robotic counterpart, in a cafeteria between pairs of trash and recycling containers. Contributions of recyclables or trash triggered directional bursts of light that gradually induced the plant displays to lean toward the more active container. In interviews, people offered explanations for the displays and spoke of caring for the plants. A marginally significant increase in recycling behavior (p=.08) occurred at the display with living plants. Apparent increases also occurred at the robotic display and a unit with only lights. Our findings indicate value in exploring the use of living material and biomimetic forms in displays, and in using lightweight robotics to deliver simple rewards.