Yes you can, but you might want to turn filtering off if you get black edges.
Ensure you load the texture with an extra ,1 at the end
load "treeTexture.bmp",1,1
Then on the object set the opacity
set object transparent 1,0
Then set the cull so the tree can be seen from behind (if using an X shape tree, or if billboard facing camera dont worry)
set object cull 1,0
Then turn filtering off if you get black edging
set object filter 1,0
Pneumatic Dryll, Outrageous epic cleric of EQ/Xev
God made the world in 7 days, but we're still waiting for the patch.