A painting that shattered auction records in 1987 now hangs behind a sheet of plexiglass that has had tomato soup thrown at it. This episode reads Vincent van Gogh's Sunflowers as a biographical roadmap rather than a decorative image. We begin in Paris between 1886 and 1888, where the first sunflower paintings showed gritty cut flowers going to seed on the ground, two of which Paul Gauguin acquired. We explain why the sunflower in particular: a revolution in synthetic pigment had produced chrome yellow, a luminous lead chromate that had never existed on canvas, and Van Gogh claimed the flower as his signature subject in an art world where others had already staked out the peony and the hollyhock.

In Arles in the summer of 1888 he painted at a frantic pace to decorate the guest room of the Yellow House for Gauguin's arrival, escalating from  ...