The glider was being launched by an automobile, and according to the pilot, '...lack of airspeed for adequate climb was generated and resulting release was low 100-150 feet.' The pilot performed a left turn 90 degrees because he did not have sufficent altitude to return to airport. He elected to land in a field adjacent to the airport. He said, 'I inadvertently deployed flaps instead of spoilers resulting in excess float.' Just before the end of the field he turned right to avoid trees. The right wing impacted the ground followed by the nose and left wing.