Marsden Hartley moved from Vence to Aix-en-Provence in 1926, at the invitation of the Kuntzes, and set to working in Cezanne’s old studio.
According to the chronology in Elizabeth Mankin Kornhauser’s 2003 retrospective, which originated at the Wadsworth Atheneum, this is when Hartley began working on Fig Tree.
The Google Books preview does not include the text about Fig Tree, but earlier texts seem to date it earlier, to 1924, when Hartley was in New Mexico. I will need to find out more about this buck wild painting, which seems to have nothing to do with channeling Cezanne.