You might be able to save some by removing the scion, check if the cambium is still green and bud hasn't begun to swell. If both conditions exist, simply move down the understock a few inches and cut a new four flap preparation, cut the scion back to green cambium and place back again and wrap again.
Jerry
Re: [NAFEX] Grafting Black Walnuts,
Jwlehman, 06/01/2006