Hi Dylan,
Peaches graft best at above 70F but you are grafting plum onto peach which has a lower optimum callousing temperature than peach scions would have. I use the below graphic that I have used for the past five years and it’s pretty reliable.
So I recommend starting once your peach rootstocks are swelling buds and your daytime highs are above 60F. Also your nighttime temps are not falling below about 50F. That will ensure that falling ambient temps during nights does not interrupt callousing. Once it starts you want continuous callousing, uninterrupted by freezing temps. You should see your grafts growing vigorously within 3 weeks.
Dennis
Kent, Wa
Callusing temperatures of Fruit and Nut trees
Posted on May 21, 2013 by qwertyqweryt61
People ask me what are optimum callusing temperatures to ensure a good percentage of viable grafts.
Nectarines/Peaches – 18-26 deg C. ( 64.4 to 78.8F)
Apricots/Cherries – 20 deg C. ( 68F)
Plums – 16 deg C. ( 60.8 F)
Apples/Pears – 13-18 deg C. ( 55.4 to 64.4F)
Walnuts – 27 deg C. (80.6 F)
Grapes – 21-24 deg C. ( 69.8 to 75.2 F).
Figs - 23.9- 29.4 deg C. ( 75-85 F).
Temperatures either side of the optimum will also work, but the percentage take will be reduced. See graph below for walnuts.
Callus graph showing optimal temperature range
