The pilot reported that during the initial climb after taking off from a wet grass runway, he believed that the airplane would not clear the trees located at the end of the runway. He further reported that he aborted the takeoff by pushing the nose of the airplane down and reducing power to idle. Subsequently, the airplane touched down hard in a nose low attitude, which resulted in a nose gear collapse and propeller strike on the runway. The firewall and both wings sustained substantial damage. The pilot did not report any mechanical malfunctions or failures with the airplane that would have precluded normal operation. The National Transportation Safety Board investigator-in-charge requested the pilot to provide the weight and balance calculations from the accident flight. The pilot could not produce a copy of the actual weight and balance, but provided the weights for the occupants and the fuel on board. According to the information provided, the estimated airplane weight and balance should have been within the manufacture's limitations. According to the manufacture's takeoff performance planning charts, the estimated ground roll should have been 1,138 feet and the distance to clear a 50 foot obstacle should have been 1,680 feet; the runway used was 3,000 feet in length with trees located at the end of the runway. The manufacturer's takeoff performance planning charts did not provide information for departing on wet grass surfaces. The Federal Aviation Administration's Airplane Flying Handbook in part states: "Soft surfaces or long, wet grass usually reduces the airplane's acceleration during the takeoff roll so much that adequate takeoff speed might not be attained if normal takeoff techniques were employed." It is likely that the wet grass increased the ground roll distance, which influenced the pilot's decision to abort the takeoff.