Have a look at a pack for Unreal (free in October) that will help you set up nature scenes.
The pack features more than 140 plant species, including 760 HQ Static Meshes:
- 648 flowers and plants;
- 28 vegetable spline elements;
- 84 environment models.
Using the pack, you will be able to create beautiful natural scenes, using flexible settings of wind and material, interaction with the character, high optimization.
It provides the ability to customize a variety of wind parameters: Waves, Swaying, Simple Grass Wind, Shadow Waves, and other aspects. There's also a system of interaction between plants and your characters.
You can learn more and get the pack here.