Children who play surrounded by elements like logs and flowers show increased levels of physical activity, according to a University of Tennessee study that looked at children's play behavior before and after their traditional playground was replaced with a "natural playscape." The children more than doubled their amount of time spent playing after the implementation of a playscape that included a creek, rocks, flowers and tree stumps.
Coe, D. P., J. I. Flynn, D. L. Wolff, S. N. Scott, and S. Durham. (2014). Children’s Physical Activity Levels and Utilization of a Traditional versus Natural Playground. Children Youth and Environments, 24(3), 1-15.