Reproductive biology knowledge of species is essential for in situ conservation, propagation and breeding. Consequently, we describe the first detailed phenology of Nothofagus alpina, mentioned until now only in general terms, and provide the morphological description of the male and female flowers. The study was conducted in 2011 in the Clonal Seed Orchard "Huillilemu" located in the locality of San José Mariquina, Region Los Ríos, Chile, at 23 meters of altitude. Observations were made in six clones of the orchard. The phenology model proposed presents ten states from the leaf bud in latency to the initial fruit. The first phenophase characterizes the leaf bud state in rest, while the second shows the morphological changes associated with getting out of dormancy. Five states described below develop male flowers and female inflorescences that appear later. The fall of male flowers mark the transition status into the female flower. The last two phenological stages describe the initial infructescence and development of the dome, respectively. These changes took place over a period of 58 days in individuals with early budding and in 40 days in late budding individuals with accumulated heat requirement of 560-623 GDD. The start date break was related to the altitudinal origin of trees, suggesting a genetic control of this feature. The overall overlap rate of flowering was calculated by 0.22, indicating low reproductive synchrony among analyzed individuals.