The pilot described entering the traffic pattern to land on the grass, which was adjacent to runway 26. The wind was out of the northwest at about 15 knots gusting to about 20 knots. The pilot said “There was moderate turbulence on downwind which increased on base and final. The glider stalled about 8 feet above touchdown due to insufficient speed for the conditions and landed hard, breaking the tail boom… My speed on base and final was insufficient for the conditions.” The pilot reported no mechanical deficiencies or mechanical problems with the glider.