The ornamental design for a gardenpillar, as shown and described.
FIG. 1 is a first perspective view of a garden pillar showing my new design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a front elevational view thereof; and,
FIG. 4 is an enlarged view of portion 4 of FIG. 2.
The broken lines in the drawings illustrate portions of the garden pillar which form no part of the claimed design.
The garden pillar is shown with a symbolic break. The appearance of any portion of the article between the break lines forms no part of the claimed design.