During the second half of the nineteenth century, the exotic South African calla lily was introduced in the United States, and it began to appear as a subject in American art. The flower became even more popular with artists after Freud provided a sexual interpretation of its form that added new levels of meaning to depictions of it. The calla lily soon became a recurring motif in works by important painters and photographers, particularly Georgia O'Keeffe, who depicted the flower so many times and in such provocative ways that by the early 1930s she became known as "the lady of the lilies."