Potentially this is a very powerful landscape genrator and has a large number of users. It has now reached version 6 ( http://www.3dnature ). . It started on the Amiga platform a few years ago, but I never got beyond the early PC versions. It is far from intuitive , has a steep learning curve and has probably not one of the best manuals I have ever seen - and I have quite a few on my shelves.
The programme is capable of very realistic landscapes and as you can see you can use lots of vegetation but it is all 2D not 3D which is fine for still images but in animations I found the results unsatisfactory when the camera was at a low level - the trees appeared to fall towards the camera.