Please advise on preparing for a forest planting...

I am thinking about doing a forest planting with some western hemlock seedlings that I saved from the lawnmower at *some point* in the future. My question is, would it be better to plant them together now or keep them in separate pots and allow them to mature and grow on their own for some time first? Is there any benefit to planting them together early on in the process, or would I be better of sticking them in the ground or something of that nature?

Thank you in advance for any advice/suggestions :)

James R.