Air layering a mulberry

I wanted to try to propagate this mulberry for a friend, and read that they could be air-layered. Basically I just removed a ring of bark about 1/4 of a inch, in early July, and then wrapped that portion in barely damp potting soil and aluminum foil. Two out of three actually formed roots. The one pictured was the best.
Now it's cut off the tree and potted up.