Yes, get a picture of the kind of tree you want to make, and use that as a template in a modeller. Make your tree as low poly as you can unles it's a feature in your game, like if you were doing a game called "the magic faraway tree" ar something, you'd make it quite detailed but if it's just there for atmosphere it could be a flat shape that always points at the camera, or have a 3d trunk and flat leaves, and just the leaves always point at the camera. You can make the leaves on a black background and just make that transparent so you only need 2 or 3 plains textured with that, and all positioned in such a way as when you look at your tree from any drection you can see enough to keep up the illusion. That's all you need to do, create a "suspension of disbeleif", no one's gonna study your tree too carefully if there's enemies bearing down on them with guns or sporks
ZX Spectrum 48k Issue 3, Radio shack Tape drive, Rank arena 12" T.V. set.