Study of reproductive patterns of understory species is of great importance because they influence the regeneration dynamics of a forest, and the biogeographic origin of these species will also define their responses to environmental conditions. In this study, we answer the following questions: Are there temporal patterns in the reproductive phenology of understory species? If so, what are the variables that influence them? How do the reproductive patterns of the species differ according to their biogeographic origin? To answer these questions, in the Abies religiosa forest in the Magdalena River Basin, Mexico City, we determined the flowering and fruiting patterns of 55 species using multivariate analyses. Spearman's correlations were calculated between the patterns found and the environmental variables, and Augspurger's synchrony indexes were also calculated. Our results showed three flowering and three fruiting patterns. The correlations showed a significant and positive relationship between flowering and precipitation during the rainy season. A significant and negative relationship was found between dry season fruiting pattern and soil moisture. The highest values of flowering and fruiting for both introduced species and native weeds occurred in different months than for characteristic understory species. Our results suggest strong relationships between reproductive patterns and biotic factors, mainly those related to species growth form and biogeographic origin. This is the first phenology study of this area, and it forms a basis for generation of hypotheses related to forest management and conservation.