What you are wanting is something that the world building program Vue does. They have coded algorithms to animate the propagation of plants which you can have a look at on their website. Trouble is it is for image rendering (films and TV).
Doing it in UE4 is another matter. I’m an artist and can tell you that it would be difficult. I could see morphing and scaling branches but the real problem is leaves… There are alot of them! Speed Tree is your first go to for help and it’s only $20 .
Please write Vue and Speed Tree with your request.