There is a tree(vegetation software called x-frog)

Xfrog also has I think 22 cd and dvds of different trees and plants which are as good as one can get to use in 3D.   They come in different formats already to use in most all major applications.
 Do search for xfrog here at Renderosity in the market place. :)

Xfrog the program you can build your own from scratch. :)

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