Why would you need free software to create trees? You got Vue already don't you? What kind of trees are you trying to make? Cause if you're just trying to get more variety than the ones in Vue your in luck cause every single tree and bush in Vue can be edited endlessly I might add. The only kind of tree that's lacking in Vue is the christmas kind. Conifers in Vue is so so and hard to edit to make look good with different branches, not impossible though.