Thanks Ocean & Casca, yes I have looked at Plant factory and will check Speedtree, actually I'm not too concern about something a bit pricey as long as is good, widely used and not too complicate to learn.
Does proxy in sketchup solve the problem even if I use many different plants of 15mb + each? to be honest I have not used the new vray 2.0 yet.
Will be nice to make like a poll to see what people here are using to deal with photorealistic vegetation.
P