It was painted in 1932.
Such a painting cannot be finished in one day, so there is no exact date.
I do not understand the question WHY. Georgia O'Keeffe painted hundreds of flowers because she was able to show how beautiful and/or interesting they are. The White Trumpet Flower is no exception.
She painted it in 1943.
'The White Trumpet Flower' was painted in 1932.
It is about a White Trumpet Flower. Dont't make things more complicated than they are!
white trumpet flower
Georgia O'Keeffe
Georgia painted her flowers as large and noticeable. she also paints "Oriental Poppies", "Blue Flower", etc.
Art Museum of San Diego.
Large and colorful
Like many of Georgia O'Keefe's flower paintings it is a realistic close-up study of a flower, yet highly personal and giving a stylized impression.
Cow's Skull with Calico Roses, 1931.
Diego Rivera painted the Flower Carrier.