The ornamental design for a lifeguardchairplanter, as shown and described.
FIG. 1 is a left side view of a lifeguard chair planter;
FIG. 2 rear view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is a perspective view thereof in an environment of use.
Flower pots and flowers are included in FIG. 6 in broken lines for the purpose of showing articles in the environment that form no part of the claimed design.