Dunno if you can change that. I dunno but maybe the "jagginess" is generated from LFS using MIP/AA/AF settings. Try reducing your MIP settings to make them more defined.
edit: And it turns out I was wrong about MIP effecting it very much. It only effects it it its a long way from the camera. Sorry.
Otherwise these are blackwoods :
WSTgrsbitATEST.dds
WSTgrsbldATEST.dds
There's many others for the other tracks. Best way to find them is use a DDS viewer - like irfanview with thumbnails viewer and a DDS plugin. Then remove the textures from the dds folder that you suspect might be a tuffet of grass. Reload LFS and see if you removed the correct dds, you will get a warning when you load the track, "file missing" and the tuft of grass will be a block of colour. Then put that single texture back and reload LFS, see if you got the right one. Do this over and over again till you discover each texture that is suspiciously resembling grass. Thats how I found the Blackwood ones. And you will see that these are probably used at West Hill as well. But check yourself. You have to do this horrid job to discover each set individually for each track. Good luck.
edit: And it turns out I was wrong about MIP effecting it very much. It only effects it it its a long way from the camera. Sorry.
Otherwise these are blackwoods :
WSTgrsbitATEST.dds
WSTgrsbldATEST.dds
There's many others for the other tracks. Best way to find them is use a DDS viewer - like irfanview with thumbnails viewer and a DDS plugin. Then remove the textures from the dds folder that you suspect might be a tuffet of grass. Reload LFS and see if you removed the correct dds, you will get a warning when you load the track, "file missing" and the tuft of grass will be a block of colour. Then put that single texture back and reload LFS, see if you got the right one. Do this over and over again till you discover each texture that is suspiciously resembling grass. Thats how I found the Blackwood ones. And you will see that these are probably used at West Hill as well. But check yourself. You have to do this horrid job to discover each set individually for each track. Good luck.