Detail this asset from Unity Store: Original Link
This is a paid asset, but now you can download HQ Photographic Textures Grass Pack Vol.1 Free.
HQ Photographic Textures Grass Pack Vol.1 v1.6
HQ Photographic Textures Grass Pack Vol.1
This Pack contains of 80 Unique High Quality Grass Textures directly settled for using in Unity 5 (Alpha Blending adjusted, Perfect Background Color & Alpha Transparency).
Most of the files are in 2K(2048×2048).
By using the Unity 5 Native Builds, Terrain Editors, Grass Shaders or any others Assets, the Textures are compatible and can be edited too in your own 2D/3D Softs.
The Vol.2 is available here.
For more informations, support:
Unity Forum Thread
Important: The Screenshots are made with others Assets, only the Grasses are included on the Pack.
Enjoy using them in Unity Games!