This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
椆 combines 木 (tree) with 周, which likely contributes the sound. The exact historical development is uncertain.
A tree 木 beside 周, but the meaning is uncertain. It may refer to a type of tree or wood.
For チュウ, imagine a tree with a chewable bark: chew -> チュウ, though the meaning is unclear.
—