Stackable plant support box

FIG. 1 is a front, top, and right perspective view of a stackable plant support box showing my new design;

FIG. 2 is a rear, bottom, and left perspective view thereof.

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a left side elevational view thereof;

FIG. 6 is a right side elevational view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

The broken lines shown in the drawings represent portions of the stackable plant support box that form no part of the claimed design.