Instantiating too much at Start? Terrain Objects.

I am trying to get unity to instantiate a lot of rocks at the start of the game like over ten thousand objects. This however freezes the game on load and it cant handle it. So now I know its not right what I am doing even if I reduce to 1000 and get it to work.

Basically I am trying to make grass, but some very large rocks and other objects with colliders on them.

All these objects have 3 level LOD on them and you can only see the really big ones from far, but LOD is not the actual cause here.

Is there some way to get it to work like in the way grass or trees works? Feels like some small thing I am forgetting? It has to be done procedurally through code.

Thanks.