We left it attached to ds for about 36 hours, until the cord was totally dry. I did have salt and lavender oil around, but it didn't smell at all. It was wrapped in one of those disposable bed liners.
Then we cut it off, dh said 'goodbye placenta and thanks for all the fish' and put it in the bin.
I liked the idea of planting it under a tree, but I didn't fancy going out in late december to do it.
I also felt it would be rather depressing if the tree then died, and given my less than stellar record with trees I'd rather not risk it.