Zelkova tree
槻 refers specifically to the Zelkova tree, a type of hardwood tree native to East Asia.
槻 combines 木 (tree) with 規, which likely contributes the sound キ. The character was created to name the Zelkova tree.
The left side 木 is a tree, and the right side 規 suggests a standard or rule. Picture a Zelkova tree as the standard for strong, beautiful wood.
For キ, imagine a key made of Zelkova wood: key -> キ, and the tree provides the strong material for the key.