The pilot made a normal approach for landing at a grass strip. After clearing trees on final, he slowed the airplane to 75 miles per hour (mph), and then he had to add power to slow his descent. The airplane touched down near the beginning of the 2,000-foot runway; the pilot estimated he had 1,800 feet of runway remaining after touchdown. After the initial touchdown the airplane bounced into the air, landed, and bounced back into the air again. At that point, the pilot was at his "normal spot for a go/no-go decision for a go-around." As he added power to go around, the airplane touched down for a third time. The pilot believed he had 1,400 feet of runway remaining. He tried to hold the airplane in ground effect until the airplane could accelerate. The pilot was not able to maintain altitude and the airplane touched down on the runway again with 700 feet of runway remaining. The pilot stated that at that point his options were limited to hitting a fence or the trees at the end of the runway. The airplane had become airborne after the final bounce. The pilot turned the airplane to the left towards a valley with "no way out." He realized that he had to pick a spot to put the airplane down, so he turned the airplane to the right toward an upsloping hill with trees. The pilot reduced the power and placed the airplane in a nose high attitude prior to colliding with a tall oak tree. The pilot reported that there were no mechanical problems with the airplane. In his written report, the pilot reported that he has had over 20 years of flying experience in a Cessna, and he was very familiar with the runway. He had also completed extensive training in the accident airplane at the accident airport. The pilot identified several different factors in the accident flight that allowed the airplane to not reach an airspeed that was suitable for a go-around; passenger weight, multiple touchdowns, and upslope of the runway.