Hello Moftkhor,
So, it looks like you are using a foliage type and then connecting that to a foliage spawner. This is then assigned to the layer you have created for your landscape.
If you open the grass type where you have your static mesh assigned there is a section to adjust the culling distance. By default it is set to max and min 0 and 0. This disables the culling completely and by default should see as far as the camera can.
By giving it a specific value you can force the engine to call the foliage up to a specific point.
These are some screenshots for visual help.
These next two are with the culling set to a smaller value.
Now, this is only if you are using procedural foliage. If you have painted your entire scene what you can do is go to the mesh where you have it assigned to your foliage brush. Click on it. Scroll down to the bottom of it’s details and there is an option there to set cull distance.
Let me know if this helps,