If you live near a forest you should consider yourself lucky. The forest is like a hobby shop for diorama supplies and everything is free! You got loads of various moss that can be used for bushes, trees etc and there are twigs all around that can be used.
And not only that, you also get the opportunity to check out the colours of leaves, tree trunks, rocks etc etc.
So if you have the opportunity to go into the forrest-do so and leave with a bunch of diorama supplies.

I was very lucky growing up because I lived in the countryside with forest in my back yard and let me tell you, there is tons of material out there. All you have to do is find it.

Sooooooo True!!! I live in a forest and spend most of my outdoor time looking down and picking up the pieces for the next dio!
Could probably start a "Hudson & Allen" type business with the stuff that lands in the backyard.
Cheers,
C.