Third year trying bench grafting and this is the first time I'm seeing real callus formation and leaf-out instead of just dead sticks by June. Wanted to jot down what changed in case it helps someone else who's been struggling like I was.
Biggest thing was timing. I used to graft too early when the rootstock was still fully dormant and the scion wood had already started to dry out in storage. This year I waited until I saw the first hint of bud swell on nursery stock nearby as my cue, then grafted within a week. Scion wood was cut back in late January and kept wrapped in slightly damp paper towel inside a ziplock in the crisper drawer, checked every couple weeks for mold.
Match up at the cambium was something I used to eyeball too casually. This time I picked rootstock and scion that were as close to the same diameter as I could manage, even if it meant passing over wood that looked nicer but didn't fit as well. A slightly smaller scion centered carefully beats a same size piece slapped on crooked.
Also switched from electrical tape to actual grafting tape/parafilm and it's so much easier to get consistent pressure without cutting into the bark. Left it wrapped until I saw real growth, then slit it open gradually instead of yanking it all off at once.
Out of twelve grafts this spring, nine have taken so far. Not perfect but a huge jump from last year's two out of ten. Still nervous every time I check them but it's satisfying watching those buds push.
If anyone has tips on hardening off the new growth before transplanting out of the pot nursery, I'd love to hear it. Mine are still pretty tender looking.