One would think a subtle (blurry) background would be easy. I had a lot of trouble with this tree. It had to be in the background but not as much as the hillside. I tried a trunk and it kept drawing my eye which is exactly what I didn't want. After scraping the trunk paint off I thought of just having the left side of the tree showing.
The background trees and bushes at the middle bottom also went through a transition. At first the trunks were a darker color but after painting a bluish purple over them and blurring the edges I had something I liked. They form another depth of field between the tree and the hillside.
The tree might look like it has a lot of detail. It has the idea of detail.
I mixed a number of colors so I had some piles of paint and started with the darkest sections making a framework. Next up were the darker greens and blues, then medium greens, and then the lightest almost mint color was last. There are a lot of passages I would go over making it darker here, lighter there, more color here. Constantly stepping back to look at the painting from a distance and deciding this or that area needs attention was essential.
Some of the giraffe's head is also painted.