Wouldnt you prefer to see them all in a main game? Hopefully you'l be able to see the trees in a demo. 
Edited:
Those trees have around 500 vertices each. I dont think its possible to go lower than that, certainly if you want to make a nice looking tree.
Edited:
Those trees have around 500 vertices each. I dont think its possible to go lower than that, certainly if you want to make a nice looking tree.