That is lovely! It is up to you if you don't intend to wash it but it would be a shame if some of the pieces came off. I think I might use one of the new invisible threads to do a tiny blanket or zig zag stitch on the edges.
You could also do your quilt sandwich and do a straight stitch through the center of the stems and at the edge of all the pieces to both secure everything and quilt it at the same time.