Instructions
Download ArmA FPS Helper and extract it to your "Arma2\addons\FPS Helper" directory. If FPS Helper is an EXE rather than a ZIP file, have it create the folder "Arma2\addons\FPS Helper."
Download and install the ArmA Launcher, which automatically detects where you have ArmA 2 installed. Start the ArmA Launcher from the start menu, then click "Options," then "Mods." Type in "FPS Helper," then select the "Arma2\addons\FPS Helper" folder and click okay. Check the box for "FPS Helper," then click "Launch Singleplayer" or "Launch Multiplayer."
Enter the game and explore a level. Foliage should be greatly diminished, particularly grass.