unity – How can I optimize my game and its game objects?

I have a 3D game in Unity and use Blender to design models for it. My game has a feature that clones an object when you click a button. An example from my game is a tree that is cloned about 100 times with different sizes and positions to a forest.

The problem is that the game really delays after a few keystrokes. Is there a way to optimize the game in Unity or the models in Blender to reduce this delay? I'm using the instantiation feature in Unity to do my cloning.