When residents plant street trees in their neighborhoods, they are more satisfied than when cities or volunteer groups plant such trees, says a UC Davis researcher. After studying tree planting in two large California cities, Robert Sommer, a UC Davis psychology professor, has found that residents who paid for street trees themselves were more positive about the outcome. Should further research confirm the findings, the results may have significant implications for the national urban forestry movement. "Giving households street trees without involvement on their part or cost may be a strategic error. This point is consistent with other research showing the benefits of active involvement in environmental change such as community gardens, user-designed parks, building renovation and neighborhood design," Sommer says in a study published recently in the Journal of Arboriculture.