Using a mesh as leaf in tree creator

I've followed this tutorial http://www.unifycommunity.com/wiki/index.php?title=TreeCreator_Tutorial I've created my leaf mesh in blender, apply a texture,move some UVs, export as .fbx and finally importing into unity. When I select Mesh as a leaf and use that leaf mesh nothing happened. Nothing happen too when I use other mesh I have, but when I use 'palm' mesh which is unity's build in I successfully got super palm tree! I wondered that what is the different between my leaf mesh and that palm tree?

Here is my leaf mesh file. (with texture) http://www.mediafire.com/?r3zof8w68o8dc3d

Thanks