How about a 'Grass Draw Distance' slider, combined with grass becoming lower quality the further away it is? That way, everyone can set the distance as far as they can without performance becoming too low for their liking, and could turn down other graphical options in order to and more headroom for grass, if they so wished.

I think the problem is that the lower LODs of the tree seem to have 'outlines' in a lighter shade of green than the rest of them. The effect of this is that they stand out against each other/the ground at medium/medium-long range. At longer ranges this effect ceases to be apparent, presumably due to the outline becoming too thin to actually appear on screen. The 'clumps' on the close-medium range LODs don't look too great either - perhaps this could be solved by keeping the trees at a higher LOD until they get further away (on higher graphical settings).