I'd like to share with you great news and a cool tutorial that is very useful to make proxy objects from your GrowFx animated trees and vegetation, so can have a very light models in scene and play the animation smoothly in viewport.
At Spline Dynamics, we've just released Q-Proxies v1.05 update, with great improvements and new features!
This tutorial shows you different techniques to generate proxy meshes for GrowFx animated vegetation, taking advantage of Q-Proxies cool tools:
Creating Proxies for Animated Vegetation
I hope you enjoy it! Cheers!