Background (grass and sky): A photo I took of a field with some low hanging clouds.
Girl writing in notebook is a stock image from Sophia A. Zhou (SophiaStock on DeviantArt - http://sophiaastock.deviantart.com/)
The Sakura cherry trees were done using the Photoshop tree generator (this class).
I painted the petals on the ground in Photoshop
Since the trees aren't exactly photo realistic looking, I ran the whole image through a process to make it look more like a watercolor painting, based on Jamie Bartlett's SkillShare class here: https://www.skillshare.com/classes/Watercolor-Photoshop-Painter-Create-Watercolor-Art-From-Photos