THE PLT LANDED IN A VACANT FIELD, APRX 1500 FT LONG, SURROUNDED BY A ROW OF TREES. BEFORE INITIATING A TAKEOFF, HE MADE A GROUND RECONNAISSANCE OF THE AREA. THE FIELD WAS COVERED WITH GRASS APRX 6 TO 9 INCHES TALL & WAS ORIENTED ON A NORTH-SOUTH DIRECTION. THERE WAS A 2% UPSLOPE FROM EITHER END OF THE FIELD TOWARD THE CENTER. ALSO, THERE WAS A ROW OF 20 FT TREES ALONG THE EAST EDGE OF THE FIELD & TALLER TREES, APRX 30 FT HIGH, AT THE NORTH END. THE PLT SAID THE WIND WAS NEGLIGIBLE, SO HE ELECTED TO TAKEOFF TO THE NORTH. DURING TAKEOFF, THE ULTRALIGHT VEHICLE ROLLED APRX 750 FT BEFORE LIFTING OFF. BY THIS TIME, THE PLT BECAME CONCERNED ABOUT CLEARING THE 30 FT TREES AT THE END OF THE FIELD & MADE A RIGHT TURN. HOWEVER, DURING THE RIGHT TURN, THE RIGHT WING HIT A 20 FT TREE & THE VEHICLE CRASHED. THE PLT NOTICED NO MALFUNCTION OR FAILURE, EXCEPT FOR A LOSS OF TAKEOFF PERFORMANCE. THE MANUFACTURER'S LISTED TAKEOFF DISTANCE WAS 75 TO 100 FT. APRX 7 MI EAST AT WICHITA, KS, THE 1649 CDT WIND WAS FROM 190 DEG AT 7 KTS.