The ornamental design for an airplantholder, as shown and described.
FIG. 1 is a perspective view of an air plant holder in accordance with the
present design;
FIG. 2 is a rear elevational view of said air plant holder; and,
FIG. 3 is a side elevational view of said air plant holder, the side view
of the air plant holder not shown being a mirror image of the side shown
in this view.