So since it's such a lengthy process to model and texture everything, I planned out the scene first with rough thumbnails, and then a quick concept to establish the general mood of the scene.
For modelling the trees branches, I modeled some simple branches using spline objects, called 'Curves' in Blender. I then used a simple particle system to place leaves onto the branches, using weight painting to establish where the leaves would spawn. I then had to rotate many of the leaves by hand so they wouldn't intersect as much. Once my branch and vine textures were made, I used another particle system that would spawn all of the tree 'parts' along the main branches of the trees, which are basically just modified cylinders. For the trunk, I modeled a cylinder, subdivided it a few times, and used a displacement map generated from my high poly tiling sculpt to push out the forms and make it look more tree like. I then collapsed and decimated the trunks since the displacement itself doesn't have to happen in real-time.
For the dock and the house, I first created a basic blockout volume of the shapes that I wanted. I then created a set of different kinds of wood pieces that I would use over and over again, which helped me cut back on the amount of texturing that I'd have to do, and also save on texture memory. I sculpted the pieces within Blender, and then using a combination of decimation and by-hand modeling, created the final low poly models. The texture baking was also handled within Blender using Cycles, and a 'synced normal map' workflow (watch this video for more info on that: https://www.youtube.com/watch?v=kGszEIT4Kww#t=531&hd=1). Synced normal maps basically ensure that your maps will look identical across apps, which is super important since nothing's worse than spending hours on making the perfect looking model, only to have it look completely different in-game. After texture baking was complete, I then ran the maps and the model through DDO, where I created a mossy wood material, which would place moss inside the cavities of the wood. I then used my final low poly wood pieces to construct the final dock and house models, keeping them all as separate objects so they'd be easy to maneuver when I had to edit things. The pieces were then duplicated and collapsed into a single object before I exported them into UE4.
That's the gist of everything, I also did a lot of experimenting with UE4's material system, which is one of the coolest tools I've ever seen. The trees, ferns and water all move on their own, controlled through their materials and vertex colors (I'll have to render off a fly-through of the scene once I figure out how to do that).
As always, if you have any questions feel free to ask in the comments below. Thanks!