How to slowly increase the size of three parts as if they are unioned

Hello everyone, I am making an apple tree. Before it can start producing, It needs to grow. However, the apple tree is made of three separate meshes, and, therefore, just changing the size would make the result look weird. Instead, I need it so that the part moves away as it grows, so it maintains the shape of a tree. How would I do this? Is there a better way to do this without scripting?

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