THE PRESERVATION SOCIETY OF Newport County, Rhode Island, is sponsoring the first annual Newport Flower Show on July 13 and 14 at Rosecliff, one of the palatial oceanfront cottages built at the turn of the century. Patterned on the Grand Trianon at Versailles, Rosecliff was constructed for Mrs. Hermann Oelrichs in 1902. During the flower show its ballroom will be decorated to suggest some of the celebrated parties she held there, including the 1904 White Ball, when all the flowers and decorations were white, guests wore white, and Mrs. Oelrichs ordered up a fleet of white dummy ships to anchor offshore. Visitors will be able to tour the rose garden, where the American Beauty rose was developed, have refreshments on the terrace, and buy plants and garden ornaments. Proceeds from the flower show will help the society restore the gardens at its eight historic mansions. For more information, call the Preservation Society of Newport County, 401-847-1000, ext. 20.