The ornamental design for an adjustable flowerbedframe, as shown and described.
FIG. 1 is a top, left side perspective view of an adjustable flower bed frame, incorporating my new design.
FIG. 2 is a right side elevation view thereof, showing only the portions visible at the right side of FIG. 1, the left side and center, connecting elements being removed for clarity of disclosure and with the broken line areas at the center of each corner forming no portion of the design.
FIG. 3 is a bottom perspective view thereof, with the top element removed for clarity of disclosure; and,
FIG. 4 is a top, right side perspective view thereof.