e_mergedmeshesinstancedist = 8

Play about with the setting, default is 8, set lower for better performance, however it will make things such as the grass animate using less frames in the distance, lower the number nearer the grass will animate less. It doesn't look great when looking over the grass at long distances but when in the grass you shouldn't see much of a difference and something like 2 will net you a smoother experience.

You can try it from the console or just put it in your autoexec.cfg.

Test it out and let me know what you think.