Observations were made of the annual growth of two cultivars of Peach tree, 'Flavortop and 'Redwing', grown on 'GF 305' rootstock at the Institut National de la Recherche Agronomique in Fréjorgues (Montpellier, France). Our purpose is to study growth rhythmicity in term of number of metamers (intermode, node, leaf and axillary production). We use the renewal process for growth modelling of axes clustered according to their architectural position. This theory can be used to estimate the time distribution between two successivé events (metamers) by using the distribution of the number of events that occur during a time 't'. This leads to a new estimation of the plastochron and its variation over a year of growth. Our goal is to apply this approach to the study of the inception of sylleptic branching, its subsequent development and the distribution of flowering.