Let's just say it.... landscapes can be boring. Yes, they teach perspective, and can meet your requirement to teach, "genre art." but, most the time they aren't very interesting.... UNLESS you look at David Hockney's landscapes!
Hockney lived in both England and the US, and his surroundings are mirrored in his work. Both the rolling meadows of England's countryside and the Hollywood Hills show up in his landscapes.
My fourth and fifth graders started by creating a line drawing using warm and cool colors to create, foreground, middle ground and background.
Then added construction paper stylized trees in cool colors.
The final product was a fabulous, "mess-with-your-eyes" optical illusion of movement and color.