Henry,
Place the pine needle image in the translucency entry and set it to 1. Also, increase the diffuse brightness. The pines were one of my first attempts at trees and they need some work.
Excellent image.
Marc
Note I'm still trying to find time to finish my Free Tree site but, I'll get it done as soon as I can. Also, you don't need to give me credit every time you use the trees. It's ok.