I can work around this issue this way, but it doesn't make me happy. The shadow chunk disappears now, if I get far enough from the fern. So it basically extends the 'render border' or what ever. To remove grass: Open Skyrim.ini look under Grass for this line: bAllowCreateGrass1. Change 1 to 0, and im sure shadows will be disabled. I have some fern which I loaded as a tree ins$$anonymous$$d of detail mesh and if I place only one little fern where no shadow is rendered, exactly this extension happens. To remove shadows: Open Skyrimprefs.ini look under Display for this line: bDrawShadows1. So I tested if I can somehow 'extend' or at least fake to extend this group or the distance. So this brought me to the theory, that the culling or the shadows of terrain trees are calculated in some kind of groups based on camera distance AND rotation. I can look at the opposite direction but if I'm close enough, the shadows don't disappear It does not just depend on whether I look at those trees but also on my distance to them. It's always a hole chunk of shadows that pop up or disappear and not individual ones

It definitly only happens with trees placed by the terrain system I just found out some things by messing around:

Skyrim turn off shadows