Download Oak Trees Package Free Unity. 

This package contains a set of 6 highly detailed PBS oak trees – each consisting of 2 smoothly fading mesh based LODs and a billboard.
The trees are manually modeled, carefully optimized, support instancing and only use 2 shared materials.

Rendering
The oak trees were created using CTI whose tree shaders support (deferred) translucent lighting, advanced bending driven by a built in directional wind zone and smooth LOD transitions. Unity’s spherical wind zones are supported only on manually placed game objects.

Compatibility
The trees have been successfully tested with Unity 5.6.3., Unity 2018.2.15 and Vegetation Studio Pro using instanced indirect rendering. A modified shader adaptor is included.
Unity’s terrain engine is fully supported.
Deferred shading is compatible with Lux Plus, AFS and ATG and needs you to assign the provided or compatible deferred lighting and reflection shaders.