This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 楤 is uncertain. It visually combines 木 (tree) with 怱, but the original meaning and component relationship are unclear.
The left side is a tree 木, and the right side 怱 looks like a hurried heart. Picture a rare tree whose fruit makes the heart race, but its true meaning is unknown.
For ソウ, imagine a soul (ソウ) trapped inside this mysterious tree: soul -> ソウ, and the tree holds the unknown meaning.