I started with a composite image:

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