can you help me?

I normally make my trees and leafs from non-living materials.

You can use real stuff, but will neat to seal them well with a varnish or similar to preserve their look and feel.
Still have a look at the local Model Railroad shop and look at the stuff that they are using in their layouts/Diorama.

I soak my modelrailroad scenery materials in Matte Medium before I place them on the layout. This soaks intothe material and preserves it. There is also a company who sells supplies for making realistic trees as well as most materials needed to do this stuff. www.scenicexpress.com

Dan Pikulski
www.DansResinCasting.com