Japanese bead tree
楝 refers specifically to the Japanese bead tree (Melia azedarach), also known as chinaberry. Its meaning is a single botanical entity rather than a cluster of abstract concepts.
楝 combines 木 (tree) with 柬, which likely contributes the sound レン. The character was created to name a specific tree species.
The tree radical 木 on the left marks this as a type of tree. The right side 柬 looks like a bundle of branches with hanging bead-like fruits, helping you remember the Japanese bead tree.
For レン, picture a row of bead trees lining a lane: lane -> レン, and the trees are laden with bead-like fruits.
chinaberry; Japanese bead tree (Melia azedarach)