Grouping multiple of same object

So I am working on a low poly planet model and as I’ve been adding many of the same objects to the scene (Like rocks and trees) I noticed that it is making the outliner very cluttered. So my question is this. Is there a way to duplicate a single object with a modifier (like a random aray) so it only takes up one object slot, or if not how to I group them after placing them so the outliner is less cluttered. This is eventually going to be a trailer that will someday with a lot of luck become a game so any advice on how to lower the pressure on the cpu/gpu would be greatly appreciated as well.

How about using particle to place objects?

The particle is the best method, however if you already have a lot of work done you could add an empty and make it parent to all the rocks and stuff. In the outliner it will all be under your empty.

Hey thanks for the tip, it was exactly what I was looking for. Worked Great!

Hey thanks for the tip, it was exactly what I was looking for. Worked Great!

Here is what I did with the particle system so far, lots of work to go. However I thought I would let you see what I was able to accomplish with your help. Thanks a lot!