For retaining wall planting, select plants that are tough and fairly drought-resistant. The soil at the top of retaining walls is generally quite dry and it can be difficult to water. Some of our favorite plants for retaining walls are groundcover Junipers, drift roses, Creeping Phlox, Trailing Rosemary, Weeping Thyme, Trailing Lobelia, Cascading Rock Cress, and Morning Glory.