Floweering and bud break of peach cv 'Springcrest' grown at three different latitudes

Observations were carried out on three commercial orchards of "Springcrest", located at different latitudes: near Udine (45° 50'), near Livorno (43° 10'), and near Agrigento - Sicily (37° 40'), recording, at 4 – 7 days intervals, phenological stages of flower bud (FB) and leaf bud (LB) until the end of flowering. It was possible to calculate the percentages and the average dates when the buds reached the following reference stages: "C" (calyx red) and "F" (full bloom) for FB and "green tip" for LB. The accumulation of Chilling Units (CU) and Growing Degree Hours (GDH) necessary to reach the aforesaid stages were calculated, comparing the effective hour temperatures with two different models, which simulate the hourly evolution of temperature starting only by the knowledgment of consecutive minimum and maximum values: a linear model (L.M.) and a sinusoidal/exponential model (S.E.M.). Great differences in CU accumulation were found in the three localities according to which model was used. When the L.M. was used "Springcrest" showed different chilling and heat requirements in the three environments, while, applying the S.E.M., produced a common value for all three stations (around 940 CU and 3670 GDH for the F stage).