get a good closeup picture of a pine tree and copy some of it so you have a little texture of just pine needles. then if you take that into paintshop or something like that, you can clean it up, make it suitable for what you're doing by making a new image, and pasting 4 of those little textures into that, rotating them so that they all spread from the centre of the image but the edges are seamless because you'll mirror each one the right way. That should do with a black background and a well Uv mapped model to texture them on.
Alternately look here:
http://www.3dcafe.com/asp/texturesplants1.asp
and here:
http://www.3dcafe.com/asp/plants.asp
They're not the greatest but it's free
ZX Spectrum 48k Issue 3, Radio shack Tape drive, Rank arena 12" T.V. set.