the shade of trees
樾 centers on the shade cast by trees, specifically the cool, sheltered area under their branches.
樾 combines 木 (tree) with 越, which likely contributes the sound and may relate to the idea of passing under or beyond, suggesting the shade that extends from a tree.
The tree radical 木 stands beside 越, like a tree spreading its shade over a path. Imagine walking under a large tree and feeling the cool shade it provides.
For エツ, picture an extra-large tree casting shade over an entire estate: estate -> エツ, and the tree's shade covers everything.