baked grass? lightmapping

Hello, is the unity terrain grass designed to not be a part of the lightmapping process?
i have my scene baked with trees, buildings (3d models), etc, but when i make my lightmap terrain grass isn’t affected. (paint details=>grass texture).

Srry for my english.

Thanks!

Export this part of terrain data as mesh. Bake and then disable it or remove from scene.