After a number of smaller forest tests with Redshift, I decided to create a more complete environment and see how much detail I could push in the scene while keeping render times relatively low.

Render Time: 13 minutes 32 seconds (1920x1080)
Hardware: i7 3930K CPU + 1x GTX980 4GB GPU

Inspired by Andree Wallin's "Swamp fever" - https://andreewallin.deviantart.com/art/Swamp-fever-192627933