THE STUDENT PILOT WAS RELEASED FROM TOW AT THREE THOUSAND FEET AGL. THE STUDENT WAS UNABLE TO FIND LIFT AND RETURNED TO THE GLIDERPORT. DURING A LOW FINAL APPROACH THE LEFT WING OF THE GLIDER STRUCK TREES. THE GLIDER ROTATED INTO THE TREES WHERE IT BECAME LODGED. THE PILOT REPORTED THE ACCIDENT COULD HAVE BEEN AVOIDED BY 'BETTER LANDING PREPARATION. [AND BY] PLANNING A HIGHER PATTERN.'