I made aluminum flashing watering collars from 6 inch tall metal. Rolls are 25 or 50 feet, so I chose to cut the lengths into 5ft sections and form a circle of 19 inch diameter. Drilled holes and pop riveted ends together. Just started using them, placed about 3 inches deep. Edges aren't very sharp but are thin enough to potentially cut children, I will try cutting old garden hose and placing over the top edge to protect the little ones. Will report back on the results in the fall. I hope they work. Attached are some photos, enjoy!