This is probably not a jonquil, but I could not find a representation of this pic to get the real flower name
I wanted to do more of the abstract qualities O'Keeffe had, especially her later works. So, this is more a Photoshop painting than anything I can tell you technically.
I cut out the background and turned the photo and cropped and cropped until I liked the composition.
I did a smart blur, fooling around until the color fields became flatter.
I changed some of the outline structure and also added more of a solid color outline.
Then, I just painted, mostly with the smudge tool. Sometimes I would sample a color from the original and airbrush it then smudge if I thought I strayed too far.
I used colors within the original to color the background, sort of a two tone with the darker in the center.
I then did an unsharp mask at 177% with a radius of 2 of the flower layer.