The ornamental design for decorative artificial marijuana wreath, as shown and described.
FIG. 1 is a perspective view of a decorative artificial marijuana wreath showing our new design, wherein the hanger is shown in broken lines and forms no part of the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof; and,
FIG. 6 is a right side view thereof, the left side view being a mirror image of the right side view.