I graft the first or second week of April onto seedlings I purchase from Missouri State Nursery 3-4 weeks in advance. I warm them up on heat mats for those 3-4 weeks and then graft. I collect the wood or have purchased scions from Nebraska Nut Growers Assc. in advance.
Of course for either bench or field grafting you should graft at the first sign of bud swell or if you are able to see the roots like in my case with these seedlings I tuck into moist sawdust in rubbermaid bins and cover with poly, then at the first sign of a white root tip is also an indicator the seedlings are ready to be grafted.
There’s no doubt field grafting has its benefits. I’ll let my friend Gary explain these benefits in this youtube video… especially grafting high into wood that is clear from deer browse.
Gary Fernald Field Grafting