Synchronous flowering and subsequent drying up of bamboos of the genus Chusquea are important processes in the dynamics and structure of many forest ecosystems. In southern South America, bamboo flowering and subsequent mast seeding trigger rodent outbreaks associated with zoonotic diseases. Predicting future flowering events requires knowledge of the age of bamboo stands together with species-specific periodicity in flowering. We explored whether it is possible to predict the minimum age in bamboo plants based on the features of their rhizomes. We studied bamboo stands of age known by the local people in 15 sites in the coastal and Andes Mountains as well as in and the Central Valley of southern Chile (37° 48'- 43° 58' S, from 12 to 1047 m.a.s.l.). For 164 individual plants, of five South American Chusquea bamboo species (C. valdiviensis, C. uliginosa, C. culeou, C. montana, and C. macrostachya), we collected and characterized the number and shape of divisions of whole rhizomes. For all species sampled there was a tight linear relationship between plant age and the number of rhizome divisions or rhizomes, accounting for 11-99 % of variation. In order to overcome constraints caused by the limited number of age cohorts available for individual species and to allow for prediction over a wider range of age, we also fitted a common linear model to species with similar age-rhizome relationships. We provide calibration relationships that can be used for retrospectively estimating the date of last flowering over large areas where bamboos form part of the understory and for predicting the future flowering events.