Potted plants are a valuable tool as they lend life to paved areas, side walks, etc. Plants must look good at all angles, and show enough detail when the camera is close as well as at a distance. Grasses, and leafy plants, such as fountain grass and agapantha are especially good, as they strike a good balance between detail, and generic form. They are both somewhat bushy, and a little lacy, which adds to the reality. They both also cast good shadows.
Trees represent a special challenge due to the number of polygons that they contain.