That's one thing I hate about the treelab in Bryce. You can't control the roots; if I want roots to behave in a certain way (like conform to my terrain, for instance), I have to either use memory-intensive metaballs or model the roots in Wings. Very annoying. One more thing you may not have thought of: if you can't find a tree photo that suits you, make a tree and then go to one of the side views. Render it fully and at a fairly high resolution (maybe 700x700 or some such, and make it square). Now don't move anything, but set the render mode to "object mask". Render again, now it's white. Now all you have to do is make a 2d face, and use your rendered tree with the white mask that you made for the image. You can have the face point at the camera for maximum effect and realism. Just a thought! =)