Japanese catalpa
楸 refers specifically to the Japanese catalpa tree, a type of deciduous tree known for its large leaves and long seed pods.
楸 combines 木 (tree) with 秋 (autumn), likely as a phono-semantic compound where 秋 hints at the sound and 木 indicates a type of tree.
A tree 木 that is associated with autumn 秋: picture a Japanese catalpa with its leaves turning golden in fall.
For シュウ, imagine a shoe hanging from a catalpa tree: shoe -> シュウ, and the tree's long seed pods look like dangling shoes.