Almond (Prunus dulcis MIll) and peach (Prunus persica L.) are closely related species with many genetic traits in common. Variation in growth habit shows a consistent pattern among populations of peach, almond and their hybrid offspring. From this material a system of growth habit traits has been identified based upon genetically controlled processes of vegetative shoot elongation and flower bud initiation. All flowers are produced from lateral buds. The classification proposed for their characterization includes:
Class I. Growth from terminal buds on one year old shoots (six morphological groups),
Class II. Growth produced from lateral buds on 1-year old shoots (three morphological groups),
Class III. Combinations of Class I and II These classes cover the entire range of peach and almond phenotypes and probably all Prunus. Class I is precocious and produces flowers by the second year from growth initiation. Class II plants do not produce flowers until the third year. Expression is enhanced by increase in vigor.