My name is Brett Robinson and I am a designer and contractor. I have developed a new landscape product called "Tree Ring Planters", that are available in 2', 4', and 6' foot diameters. The install quickly with no digging and you fill them with your favorite mulch or decorative stone. Low profile so your mower goes right over them so no string trimming required. They are being manufactured by the "DeWitt company", a manufacturer of many landscape fabrics and other landscape products.
