I have done quite a bit of spring grafting of peaches. They are one
of the hardest fruit trees to graft; they seem to be picky about
everything. Over the years I have found a technique which gives me 75+
% success, and so by doing several backup grafts of every variety I
manage to get a take on them all.
1) Graft when temperatures are forecast to be in the 70's highs and
50's lows for the next week. This is the most important, they seem
very picky on the temperature. You don't have to be completely
perfect here but the closer to this approximate range the better. I
usually do two rounds of grafts a week or two apart to improve my odds
here.
2) Use parafilm (or other method to keep from drying out) over the
graft as well as the whole scion. My personal method is parafilm on
the graft and doc farwells painted on the scion. Sometimes this is
not needed because the grafts will take very quickly, but most of the
time they will require a lot longer time than say apples and so you
need to give them some help to stay alive.
3) wrap over the whole graft in aluminum foil, shiny side out. This
helps to stabilize the temperature, particularly if the graft is in
the sun.
4) Use very vigorous stocks. This helps all kinds of fruits but you
need all the help you can get for peaches.
I usually do whip and tongue if the scion/stock sizes match, and bark
or cleft graft if the stock is bigger. I sometimes do chip or T buds
for the backup grafts, on an existing tree limb of around pencil
diameter. For some reason my buds on fatter stocks nearly always fail.