A slope guard device having one or more panels formed of impervious material, interlocking along their periphery to form a rigid annular unit capable of encircling a planted area on a slope. The panels define an inner side adjacent to roots, and an outer side remote from roots, said panels of varying heights to allow a user to customize a slope profile to a slope where taller panels support the slope above the planted area. Vanes extend from the panels and project inwardly from the inner side of the panels. The vanes direct root growth. Vents are attachable to some of the vanes each having an open upper end and open lower end, said vents providing additional structural support for the slope guard. The vents guide steel stakes that can be driven into the ground.