Creating Trees and Foliage

Hey guys, so I’ve been wanting to create some foliage for my game, such as bushes and flowers and whatnot, but now I’ve noticed that I need to create trees as well, because they just don’t seem to get tall enough for my game scale[pic included]. What program/method do you suggest for creating new trees and other scenic objects?

There are some guides in the Unity documentation, and also a tutorial on the Unify Community Wiki :