Bonsai Tree 

The japanese art of growing dwarfed, ornamentally shaped trees or shrubs in small shallow pots or trays.

My flower pot has a tree in it, a bonsai tree.

Bonsai Tree by Louis Waweru December 5, 2003

Someone else's bonzai tree 

Especially relevant in big companies. When you develop an intricate, sought after skill set, but never rise to the level that was possible from your early potential, that may have been/still could be achievable elsewhere.

Zach has a PhD from an ivy league college, and has built enviable experience, but has never risen above director level in the blue chip company he works for. He's become little more than someone else's bonzai tree, and should probably leave, in order to become a red wood.

Someone else's bonzai tree by RandyRhoads84 October 23, 2023