The pilot reported that he was landing the twin-engine airplane on the 2,845-foot-long, hard surfaced runway, which was bordered by trees. After the airplane cleared the trees on the approach, he “…pointed the airplane down.” Approximately 50 feet above the ground the pilot began a flare for landing; however, the airplane did not respond and continued to descend at a steep rate until it impacted the runway’s displaced threshold. The airplane subsequently veered off the right side of the runway. During the accident sequence, the right main gear and nose gear collapsed which resulted in substantial damage to the right wing and empennage. The pilot later reported that he allowed the airplane to get too slow on approach. The pilot reported no mechanical failures or malfunctions with the airframe or engine that would have precluded normal operations.