First create a new blank layer
Then run Filter>Render>Tree
After that you can use the Move Tool to move or scale the tree
Press V on the keyboard for the Move Tool
some tips about using the tree filter
Thanks for that. I can move the tree, but how do I scale it ?
Got it ! Spotted SHOW TRANSFORM CONTROLS at the top . . .
I also believe you can create a rectangular marquee the size you want, and the tree will fill it according to the min dimension. so if you want a tree a certain height, make a marquee very wide, but the height you want. I would be best to scale the tree as mentioned above through - put in a smart object for future adjustment.