Free low poly trees for architectural visualization
In every article that I have the opportunity to talk about trees and shrubs for architectural visualization, I always recommend the use of textures to simulate and populate a scene. They give great results without big loads on the scene performance. But, if you need geometry based trees to use on your projects, then the best solution will be to import and use low poly trees to avoid those load problems. For these situations, I found a great resource with free low poly trees and shrubs aimed for game projects, but we can use them as well.
The site is called Loopix-Project and you will find the trees at the freebies section.