Abstract: A tree root deflector is installed in a ground planting location between a tree and a sidewalk or other static structure for training tree rootlets downwardly so as to emerge beneath the deflector for subsequent lateral growth and enlargement at a safe depth beneath such structure. The deflector includes a plastic panel having a plurality of vertical root deflecting ridges protruding abruptly from the tree side of the panel at horizontally spaced apart locations for deflecting tree rootlets downwardly, as well as a plurality of transverse abrupt ridges protruding from the same side of the panel at horizontally spaced apart locations disposed intermediate the vertical ridges to lock the panel with the tree roots and with the ground, the transverse ridges being relatively short so as to leave substantial spaces between them and the adjacent vertical ridges.