Seeking Environment Pack for Open World Pacific Northwest Scenery

I am looking for recommendations - marketplace or otherwise. I am building an open world type game based in the Pacific Northwest. I am looking for a suitable addon scenery pack with terrain materials, procedural foliage, grass tool, including seasonal variations. I am looking for rock, fir trees, ferns, grass etc. I am new to the marketplace and am probably not looking in the right place - all suggestions welcome.