Moss Phlox | Plants from Bakker Spalding Garden Company Walls and Ground cover Evergreen Moss Phlox grows well in the ground. The top of the root ball should be just slightly below ground level. This plant grows best when placed in complete or partial sunshine. Moss Phlox bloom from spring until late summer. Moss Phlox is great for hanging over walls or planting in the rock garden. It forms a dense mass and therefore makes a great ground cover.