Later, but this should do.
The two seedlings I have now were both self seeded. Both in pots sitting on the patio under the big acer. The soil in each is from the garden compost.
The one I moved on is in a bigger pot full of acer-specific material (I think it was John Inness number two - but...
I have two on the go. One I have potted up and it seems to have been transfixed into a stupor. One I potted up last year conked out in the late summer. The other is where it self seeded. I am inclined to leave it there, even though the pot has a golden rain tree seedling growing in it.
Any...