What was the title of Georgia O'Keeffe's first large-scale flower painting?

Georgia O'Keeffe's first large-scale flower painting was Petunia, No. 2.

O'Keeffe painted Petunia, No. 2 in 1924, enlarging a single flower so that its petals fill much of the composition. The painting is an early example of the close-up flower images that became central to her public identity during the 1920s.

She had begun painting flowers on a large scale because she wanted people to notice their beauty. Her flower paintings are often interpreted symbolically, especially through comparisons with the human body, but O'Keeffe repeatedly resisted fixed symbolic explanations. Petunia, No. 2 should also not be confused with Jimson Weed, her famous 1932 flower painting, or Black Iris, a later work from 1926.