The pilot reported that, during the approach, the airspeed was about 80 knots, but he was slightly high. The pilot stated that the airplane floated down the runway further than normal before it touched down, and when he determined that he would not have enough runway to stop, he aborted the landing. The airplane did not climb as he expected, and subsequently impacted trees. The pilot added that he believed that the reason for the lack of climb was due to his failure to retract the flaps to 50%. A witness reported that the airplane landed further down the runway than normal, departed the runway, and began the takeoff from the grass alongside the runway. The airplane sustained substantial damage to the left wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.