A quick-and-dirty collage of the evolution of background designs over the show’s run, focusing on Sweet Apple Acres and trees in general.
 
The top two rows are from the early-to-middle seasons (1 to 3 on the top, 3 to 5 on the bottom). Trees start out with very stylized, apple-shaped crowns and no shading. The trunks and branches are also fairly simplified, but have some more detail. The overall look is rather “flat”. Some shading and leaf details are added in more scenic shots.
 
The bottom two rows are from the late seasons (6 on the top, 8 and 9 on the bottom). Shading and leaf details become much more common and are almost always present. Trees very close to the viewer are drawn with more complex trunk, branch and canopy shapes, with a far more three-dimensional appearance; background trees retain the older apple-shaped outline.
 
Season 9 adds shading to the trunks as well. The work put into individual trees increases over the show’s run; Season 9 has background trees with more detail and shading than ones in the focus of the early seasons’ more elaborate shots; foreground scenery is much more unique and elaborate.
 
The coloring and lighting undergo a similar evolution. Compare the dawn/dusk shots in Season 2 (top, right), Season 6 (bottom middle, left) and Season 8 (bottom, left).